2002-03-08 Nice - if you're a historian

..Every physicist learns to respect and look up to the legendary figure of Dirac. Also, sooner or later, every physicist hears about Dirac's "elegant" book on QM. Some courses list it as a reference.
However, there are several reasons to avoid this book as a source of knowledge and/or learning. These are:
1.) It is outdated. The introductory chapters on QED (the last ones in the book) have long since been outdated. No one thinks of field theory that way anymore.
2.) It is mathematically sloppy. Dirac introduces the Bra and Ket notation (for which he is responsible, by the way) without mentioning the dual space, and sometimes even reasons wrongly; i.e., he writes "let us postulate that for each ket, there exists a corresponding bra" - this is not a postulate. This is ALWAYS true for finite dimensional vector spaces, and NEVER true for infinite dimensional vector spaces, and can be proven mathematically. In short, there is little attention given to the mathematics behind QM.
3.) Dirac wasn't a pedagog. There aren't any solved examples, and his treatment of many topics is much, much too brief - about 2 pages for the Hydrogen atom? A page for angular momentum? Three for the harmonic oscillator? Come on, to understand these things one needs to see them from many different perspectives, and Dirac's way of doing things is taking the shortest route between two points (which is why he is often described as "elegant") - this doesn't afford the reader the opportunity to get to know these topics in depth.

This book can only be of interest to people who are interested in the history of QM or would like to hear a great physicist's way of viewing it - which isn't always different from the usual interpretations you get exposed to in more contemporary literature.