In many ways, this is still my favourite quantum mechanics text. Why? Because the text is completely grounded in the quantum mechanics of atoms and molecules.
Historically, Linus Pauling spent his post-doc working throughout Europe where he absorbed the, then, new theory of quantum mechanics. However, the physicists that he learnt q.m. from only analysed the physics of, relatively simple, atomic systems. It would require someone with an immense breadth of knowledge in chemistry to make quantum mechanics come alive for molecules. This was Linus Pauling. Pauling first applied q.m. to such diverse topics as: the chemical bond, resonance energy, electronegativity, crystal structure of molecules and hydrogen bonds.
And it shows. The uniqueness of this q.m. textbook is that it gives immensely detailed references to the different ways the early physicists/chemists attacked the q.m. of bonds in molecules. Many different ansatz's and approximations to pertubation problems are given. And Pauling should know, for he was right in the thick of it. The historical value of these references alone is worth the price of this book. It's a real shame that most modern books leave these out, because a discussion of these approximations methods give a lot of insight to q.m. in molecules.
In contrast, I find modern textbooks on physical chemistry to be often lacking in deep physical insight. However, textbooks written by physicists run into all sorts of esoteric directions like quantum entanglement and the uncertainty principle and as a previous reviewer noted, Pauling's books says nothing about scattering and hardly anything on spin. This is probably because chemists aren't interested in what happens to particles in beams or Stern-Gerlach experiments. They are more interested in ionisation energy, enthalpies and bond energies.
Nevertheless, for out-and-out modern-day quantum physicists, Pauling's explanation of aspects of quantum mechanics will seem quaint, overly pictorial and concrete, e.g. discussion of *actual* orbits. And it is. However, for chemists and even atomic physicists, pondering such esoteric questions clouds the immense power of quantum mechanics in explaining the detailed properties of atoms and molecules.
