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A good gentle introduction to assembly language programming for the 6502 processor. This processor was used in many retro computing and gaming platforms, including the Apple II, Commodore VIC-20 and 64, Atari 2600, Atari 800/XL/XE, NES, and more - so if you're interested in developing homebrew for one of these systems, this book is still relevant.

The book is strong in that it tells you which 6502 instructions are really used often, and which ones are used for specialized purposes. It has a good explanation of the processor's addressing modes and how memory is accessed. It tries to avoid being specific to one type of machine architecture, so you can benefit from this book no matter what type of 6502-based machine you are planning to develop for. But if you are developing for Commodore, Apple or Atari systems the book includes a simple type-in assembler and disaassembler (written in BASIC), so you can type in and try out example code.

One thing that really dates the book, however, is that it assumes you are an accomplished BASIC programmer, and tries to explain 6502 programming in terms of BASIC. This is perfectly understandable given the era. In 1982, the author was targeting his audience well. Today, the references to BASIC are a bit of a distraction.

Finally, this is an introductory book, and leaves out a serious discussion of math on the 6502, specifically working with negative values, ones-complement and twos-complement binary. It shouldn't be the only book you read.