As the title suggests, this is essentially a reference guide to programming the 6502 CPU. The book starts with the usual chapters describing the registers and the different addressing modes, but the bulk of the book is devoted to a comprehensive description of the complete 6502 instruction set. This also includes some useful information on timing. I would have liked longer examples showing the use of each instruction in a relevant context rather than in isolation, and diagrams showing how the bits are shuffled around between and within the registers.

Personally, I still prefer my older 6502 Assembly Language Programming by Leventhal (published by McGraw-Hill), a larger, more comprehensive and slightly more expensive book. The 6502 Reference Guide by Alan Tully is a good (and cheaper) runner-up.