This book is an excellent reference/tutorial for anyone interested in the inner workings of Atari BASIC. It was written by Kathleen O'Brien and Paul Laughton, who wrote almost all of the source code, and Bill Wilkinson who may be familiar to you for his articles in COMPUTE! magazine.
Included is a complete description of how Atari BASIC stores, retrieves and executes programs, how to access BASIC directly (accessing BASIC from
BASIC?!) and a completely disassembled and well commented listing of the source code for BASIC and the built in maths ROM. As if that were not enough there is also a section on some of the bugs in BASIC, why they occur and even how they could be fixed! It carefully explains nearly every step of the interpreter from when it coldstarts to when it reaches END in a BASIC program. It also explains how BASIC stores numbers, strings and arrays, how it arranges memory, even how it converts a line that you type in into a form that the machine can understand.
Often books of this nature are spoilt because the authors automatically assume the reader has the same level of understanding of the subject as they have or, even worse, do not seem to know what they are talking about. This is certainly not the case here, this was obviously written by someone who knows their subject inside out which is not after all surprising if you consider their backgrounds. Although much of what the book contains is of a technical nature and is therefore pitched at the
reader with a reasonably good knowledge of BASIC and at least some knowledge of machine language, it is well written and easily read.
In terms of its usefulness, well I think this is a case of an answer looking for a question! At one level, several of the routines may well be useful for your machine code or advanced BASIC programming and at a much higher level you may well want to create your own language using the routines in Basic as a starting point.
Either way, this is an excellent book for the intermediate to advanced user, not only as a guide
to the inner workings of BASIC, but also to how language interpreters work in general. It is not a
book for the beginner but if you feel like delving deeper into your Atari then this book is
extremely good value for money.