It's an excellent book for learning about USB in general, but it doesn't offer much on the PIC side. It does have a simple PBP interface example for a 16F877 & FTDI USB/Serial + USB/Parallel, but not for a USB PIC.

I learned a great deal from this book. It has Visual Basic & Visual C++ code examples, and goes into nice detail on how USB works overall. Explaining how the host functions, USB protocols, terminology, USB hardware & power options, and a good deal more.

As for learning about the USB PIC, I got more out of the Microchip USB framework code written entirely in C than anything else. The C framework is documented pretty well, and explains a lot of the low-level USB details the 18F4550 data sheet is kind of vaque on.

If you plan to do much work with USB, it's worth the investment. Browsing through the Microchip USB C framework code will answer a lot of questions.