I think I will start giving my thoughts on physics books and textbooks in this blog. I hope this will help people decide whether they want to read the books. Note, though, these won’t be chapter-by-chapter reviews. They will be intentionally concise.
For my first review, I chose one of the most well-known modern textbooks: Introduction to Quantum Mechanics (3rd ed.) by Griffiths and Schroeter. The first two editions were by Griffiths alone, so some, including myself, refer to the book as “Griffiths”.
When someone on Reddit asks for a text to self-study from, I see Griffiths suggested quite a bit. I do not endorse this book for that purpose for most people. Allow me to explain why it is too specialized and difficult for the average person.
Not a book for lay people
First, the text focuses heavily on the math without sufficient insight into the physics. By this I mean that the book contains general mathematical techniques that are essential for solving quantum mechanical problems and they do relate to particular topics, but one does not walk away from this book with a good overview of, say, atomic or nuclear physics. For optimal learning, one should first have an overview of those fields and then follow it up with the deeper math of this book. I think many physicists and physics students have the “curse of knowledge” and can’t see how difficult it would be for a layperson to learn from this book.
Secondly, Griffiths has hidden many math and physics facts inside the end-of-chapter problems. The reader must then be able to properly complete the problems to learn. The average Redditor is not going to be able to do them because this textbook is meant for a third-year physics student to learn from. These students already know calculus and have completed courses on modern physics and classical mechanics.
Two more issues
The above two points are relevant for laypersons considering attempting this book. The next two points are general points against the book that even students and professionals should be aware of.
I can say that Griffiths teaches, more or less, the postulates of quantum mechanics. But the delivery is spread across many chapters, and the importance of knowing the foundational ideas as a whole is not there. A student reading this textbook would be hard pressed to articulate them all.
Now, I must say that, from my book, you will find that the postulates do not create a flawless or complete axiomatic system. Despite that fact, I think it’s important to know them well so that they may serve as an organizational framework to understand quantum mechanics.
I claim they are important to know because I can see physicists who slip up precisely because they don’t know this framework. For example, by how these physicists explain what is known as a commutator, they must think that “applying two operators to a ket in succession corresponds to two measurements.” This is not true because in the accepted mathematical formalism of quantum mechanics, there is usually randomness involved in a measurement. But the operator algebra has no randomness: we know exactly the result from their application. Therefore, the made-up quote above completely misses out on randomness.
Another thing Griffiths does is make it seem that the currently accepted mathematical description of quantum mechanics doesn’t violate conservation of energy. The claim is in many places throughout the textbook. But, since I am in the know, I questioned what exactly he meant by this.
I might as well quote myself to show what I found. It’s rare for the entries in my bibliography to have notes, but here is one of the exceptions (p. 396):
A warning: A quick scan of Griffiths (and Schroeter) will make it seem like he believes in the full version of the conservation laws. He has dozens and dozens of mentions of conservation that make it seem this way. However, at best, he is inconsistent. At worst, his is the weak version of conservation. On page 112, he says “Nowhere does quantum mechanics license violation of energy conservation, and certainly no such authorization entered into the derivation of Equation 3.76.” But, on p. 30, in the context of the probabilities of getting particular results in experiments and expectations values, he tell us that “These are manifestations of energy conservation in quantum mechanics.” Therefore, his version of energy conservation only works on an average over measurements. At the end of the book, he states something which reinforces my assessment: “In this book… particles do not in general possess specific dynamical properties (position, momentum, energy, angular momentum, etc.) until an act of measurement intervenes”.
So, stitching together the explanations from those page references, according to Griffiths, energy is not conserved in individual interactions, but is conserved on average. All his other phrasing does not reveal this.
There are other things I could explain, such as the three different explanations of a Dirac delta (i.e., the correct one, the “infinite” impulse one, and the complex exponential one). However, those perhaps are too much for a book review. Besides, I briefly mention three of them in my book.
Who then is this textbook for?
With all that out of the way, who should buy this book? Well, I developed a fondness for his writing style when I learned from his electromagnetism textbook, so I bought his quantum textbook as one of the books I used to fact-check myself while writing my book. And, it was rather useful to me.
Regarding self-studiers, I think someone with, say, a background in engineering or computer science who is very motivated to try most of the end-of-chapter problems will come away able to intelligently talk with physicists and understand much of certain papers in physics journals.
If a professor uses this book in a course on quantum mechanics, I would not tsk-tsk them. It’s alright as a classroom text for physics students. They will get the same education as the average student. And I think this is where the book should be used in most cases.