. To Arjun, the PDF version he’d been squinting at on his phone was nothing compared to the weight of the physical book. By the time he reached the chapter on angular momentum

Chapters 1–3 cover the origins of quantum theory (Planck’s hypothesis, photoelectric effect, etc.) and basic wave mechanical concepts.

The book covers the standard progression of quantum theory, with the Second Edition adding more advanced modern topics. Amazon.com Foundational Quantum Theory

If you cannot afford the book and your library does not have it, I highly recommend these :

If you are a student with financial constraints, use the library or a legitimate low-cost e-book. If you can afford the ₹600 paperback, buy it—you will want to throw it across the room in frustration, then pick it back up because problem 3.17 is due tomorrow.

Introduction to the Klein-Gordon and Dirac equations. Accessing the PDF