I had been teaching Chemistry, Physics and Mathematics since I was fourteen. I have initially taught Chemistry classes for children aged 12-16 at a local youth club in my town called Young Folks LV for a year, after which I proceeded to teach private tuition for STEM subjects as well as coaching (both official camp and private) of Chemistry Olympiad participants.

Currently I'm teaching the national teams of Estonia and Latvia for the International Chemistry Olympiad (IChO) as the preparatory camp lecturer on Physical Chemistry. You can find a recording of one of my lectures on Thermodynamics here. The lecture notes with exercises are also available.

I have prepared a list of readings I read myself and can wholeheartedly recommend to people studying for Chemistry Olympiads and beyond. You might be interested in checking it out as well.

I am also a Peer Tutor in Chemistry in NTU Division of Chemistry and Biological Chemistry, where I continue to maintain my teaching skills. You are free to reach out to me if you need any tutoring or such advice.

I assume you came here to search answers to the question "What shall I read to learn chemistry/participate in my regional or national Olympiad/get IChO medals/proceed to going to serious topics in university?" This is a compilation of some books I read myself with some advice on how to read them.

All things that pertain to studying theory of whichever natural science including chemistry should be divided into two categories:

- Knowledge (actual maths behind, heavy on concepts; for example symmetry idea in MO)
- Skills (actual problems, should yield an algorithm of doing a problem, i.e. how to identify symmetry group for a given molecule).

For the knowledge part there is some theoretical minimum of understanding that is needed to be able to apply whichever skill relevant to IChO. It is found in all years and should not appear in the preparatory problem set for the organisers to expect your familiarity with them:

- High school maths (including geometry)! All PChem and inorg are very much totally dependent on the student’s proficiency in maths and their algebra.
-Basic understanding of physics (at 9th grade level, so that you understand what is a force, Coulomb's law, difference between potential and kinetic energy…)
-Redox and electrochemistry on a qualitative level
-Intro to crystal structures (with thermodynamic justification why they don’t fall apart)
-Intro to MO theory
-Intro to chemical thermodynamics (at a level of understanding 4 laws and G,H,S.F,U)
-Intro to kinetics
-Intro to acid-base reactions
-Intro to equilibrium calculations
-Arrow pushing for orgchem (nucleophile. electrophile etc)
-Intro to spectroscopy (electronic properties affecting the shape and position of lines)

Meanwhile, examples of skills needed in the olympiad exams include:

-Algebra! I cannot stress enough that total fluency in high-school algebra is a must for all inorganic and physical chemistry problems. Involves being able to express something from a formula, being able to solve equations that have elementary solutions (this includes large algebraic systems), being able to manipulate exp/log functions and use trigonometry.
-Cartesian geometry in 2D and 3D (crystal distances, visualising 3d organic molecules)
-Balancing equations, predicting inorganic products
-ABC problem solving algorithms
-Identifying reactants and characteristic transformations on organic scheme
-Drawing thermodynamics cycles and related calculations
-ICE tables and equilibrium
-Nernst equation and electrochemistry calculations
-Understanding which approximation for a kinetic scheme should be used in which cases
-Reading spectra
-Identifying stereochemical descriptors
-Calculations for crystal structures

Basically, if for your topic there exists some algorithm for how problems on that topic are solved, this is a skill, not knowledge. Skills without knowledge are more beneficial than knowledge without skills at IChO level (up to advanced undergraduate level, but more on that in the undergraduate reading list). You can easily get a silver medal in IChO with zero knowledge but good skill. This syllabus is the author’s own opinion on different levels of knowledge (IChO bronze/low silver, IChO high silver/gold, University undergraduate, Graduate school) and different skill sets (for IChO bronze/low silver, IChO high silver/gold) with practice problem suggestions that might help you study for the olympiad and to then progress towards doing actual science in the field.

P.S. The author himself personally has read/is currently reading every book they endorse on this page.

Best read the books in the order listed, but you can read them in parallel.
Without those books, only having skills will be quite detrimental because you would have no understanding on why problems are solved this way. Those books are a total of around 1.5k pages, and they should be read like a novel, not a textbook. So you can just sit down on a sofa with a cup of tea and read it like a novel; a 1.5k page novel is easily readable in a month’s time during free time of a busy working person, so you as a student can reasonably get all the theory you need for IChO gold in a month of sofa reading (for example during summer break).

If you don't read all of those books I wouldn’t guarantee you even get a HM for the olympiad.

Just practise sofa reading until you are done with all three of those books, then you can begin improving on your skills. Try to enjoy the process because those books are not scary and you can easily read them as a pastime.

-Glinka: General Chemistry Vol 2 for inorganic chemistry.
-Wothers: Chemical Structure and Reactivity for general chemistry.
-Clayden: Organic Chemistry (up to the carbenes chapter) for organic chemistry.

The books in this list are actual textbooks from undergraduate courses of study.
You have to switch your reading approach from “Read like a novel” to “Read with understanding; maybe some note taking for the hard things”. At such a level you should teach yourself how to make good notes for a textbook! They must not be just quoted parts of the book!!!
Do not read the above mentioned books unless you have a sufficient skill set for doing IChO problems on a decent silver medal level. They are going to take up a lot of time but are definitely worth it in the long run because you would have to read them during university anyways. Those books cover most of the advanced topics of the preparatory problems syllabi, and should be studied only as a “knowledge for the advanced topic” sort of reading. They will not substitute the solving skills you should focus on for the exams! Greenwood is a must if your national selection is hard on ABC problems. Otherwise you can continue reading Greenwood on your sofa which you should have mastered by now if you are reading this list. Greenwood is a very nice book for reading on the sofa.

-Housecroft: Inorganic Chemistry (chapters 1-9 and the CFT chapter) for advanced PP inorganic topics.
-Clayden: Organic Chemistry (the remaining chapters) for biochemistry and organometallics advanced PP topics for organic.
-Engel & Reid: Physical Chemistry (chapters 1-6, 11, 35. Third edition, 4th is bad) to cover advanced topics for physical chemistry in PP.
-Greenwood: Chemistry of the Elements (sofa reading) for a lot of inorganic chemistry facts for ABC problems that you won’t need unless you do Russian or Chinese olympiads.

If you have reached this far, you are most likely a fresh IChO medalist studying in a university.
You might have noticed by now that the approach of everything shifted drastically — you don’t need as much skills compared to knowledge at this point. A good little comparison is the popular game Factorio: the main two resources are iron (skill) and copper (knowledge). In the early game (IChO times and first years of undergraduate) you need significantly more iron than copper to sustain all the basic buildings and such. When you reach the late game (late undergrad, graduate study and thereafter) you end up spending way more copper than iron due to the need of advanced production with an already existing backbone.
The first two years are very easy to score straight A's on the exams just because of the way the exams work. Exams are still about skill. You would have to study the bare minimum skill to pass exams unless the subject relates to the area you are actually interested in, those are the areas where you should be working on your skill in internships/research, not by solving problems.
On the other hand, knowledge remains super important for you, this is why you should read more serious knowledge-focused books that give you more rigour for understanding the scope and applicability of everything you learned beforehand. Again, somewhere here you have to take the final decision if you want to pursue the synthetic chemistry or theoretical chemistry route if you want to remain in the field of chemistry altogether.

Theoretical chemistry

-Pauling: General Chemistry. The book is old but Pauling is one of five people to have two Nobel prizes. The book is very much worth it, plus you can buy a hard copy for 20 dollars from Dover.
-All the previous readings mentioned in IChO advanced readings.
-Spivak: Calculus. Yes, it is hated by many as the first calculus book for being a book packed with proofs. If you already decided to do theory, proofs will become a part of your life; Spivak is a very very good calculus book to gain intuition. Train on the proofs now. You might combine Spivak with Abbott (from the next chapter) for proof exercises. Do not read Calculus on Manifolds yet.
-Rosen: Discrete mathematics with applications. If you suck at proofs, check out the exercises in the first chapters to train on easier proofs before Spivak.
-Пантаев: Матанализ с человеческим лицом. It also covers complex analysis and multivariate calculus as an added bonus. Basically Spivak but in Russian. Choose between this and Spivak for calculus, I recommend Пантаев if you can read in Russian.
-Demidovich: Problems in Mathematical Analysis (or literally any other calculus problem book on this level). Demidovich is good because he goes from super easy to super hard. I would say the best opinion on maths for theory in chem is the level of maths you needed to get into Landau’s graduate school in the 1930s: being able to do integrals in your sleep. If an integral can be expressed in elementary functions, you should be able to do it. This is a skill you must master before you begin doing more serious physics stuff.
-Susskind: The theoretical minimum: All you need to start doing physics for an introduction to how real physics works. Susskind himself said the book is basically Landau Vol1 but watered down in the preface to that book; it is completely true. It will prepare you for the meeting with Landau’s own books a bit later.

Synthetic chemistry

-Pauling: General Chemistry. The book is old but Pauling is one of five people to have two Nobel prizes. The book is very much worth it, plus you can buy a hard copy for 20 dollars from Dover.
-All the previous readings mentioned in IChO advanced readings.
-J Field: Organic structures from spectra. This book is sufficient to cover almost all the needs in spectroscopy that may arise. It also has 500+ problems on basic spectra going up to 2D and 3D NMR.

At this level you are probably already decided on the topics you have a passion for. You are a 3rd/4th year undergraduate who has secured some sort of research opportunity or industrial experience. You should begin studying the specific topics that relate to your research, but some sort of theoretical minimum still exists for the synthetic and theoretical pathways. Those are fundamental books that will make you reconsider all things you learned before. You would gain a much stronger understanding of the fundamental concepts and, most important, the scope of applicability of different theories of chemistry and physics.

Theoretical chemistry

-Abbott: Understanding Analysis. Use it as a proof exercise book. Do note the book is for mathematicians, and I'd rather study real analysis from Nikolsky.
-Nikolsky: A Course on Mathematical Analysis. The author lived for 107 years, 80 of them he was teaching real analysis for physicists. This sole reason talks how competent he is. I like the book for being very rigorous but very applied, so it gives all rigour exposition of real analysis without the occasional useless functions mentioned "for fun" by such books for mathematicians.
-Callen: Introduction to Thermodynamics, for a rigorous introduction in classical thermodynamics.
-Борщевский: Физическая химия: Химическая и общая термодинамика. Undoubtedly the best book on chemical thermodynamics ever written. If you can read in Russian, this is a must-read! Be aware that both Callen and Borschevsky will totally explode your brain and hard reboot your understanding of thermodynamics.
-L Landau, E Lifshitz: Course of Theoretical Physics, (aka THE COURSE), Volumes 1,2,3,5,10. Yes, another time I recommend Landau. This book is a masterpiece. Reading Vol 1 initially feels like having your skull smashed with a hammer. Vol1 is a complete overhaul of classical mechanics from the viewpoint of energy (so you deal with Hamiltonian/Lagrangian mechanics without a single mention of F=ma throughout the entire book); Vol2 which you should read until the chapter on optics is a complete overhaul of electrodynamics with very important conclusions for you as a chemist; Vol3 is one half general quantum mechanics, other half MO theory and NMR from a rigorous explanation standpoint. Vol5 is amongst the best books on thermodynamics published by far. Vol10 is a book on kinetics. Do note the style of Vol10 is different from the others because it was published after Landau’s death by his students.
-Kostrikin: Introduction to Algebra. I liked the English edition more than the Russian original (Кострикин: Введение в алгебру в трех томах), although both are very good. Group theory is written very well; without that you are going to struggle for QChem. I would recommend to read it after the first exposure to Landau, though.

Synthetic chemistry

-Carey & Sundberg: Advanced Organic Chemistry, part A is a very interesting read that correlates physical and computational chemistry to actual synthetic results; part B is basically an independent book on advanced arrow pushing and lots of interesting synthetic approaches.

As you see, I do lack the amount of books in advanced synthetic readings. If anyone who read enough advanced synthetic chemistry books to have their own minimum reading recommendations wants to give me their suggestions, you can always email me!