The first stand-alone book is Mastering Machine Code on Your ZX Spectrum by Toni Baker. Former owners of ZX-81s may notice that the book is an update on Interfaces ZX-81 machine code book. The contents are similar to the earlier version, although the Spectrum book is longer because of the introduction of extended chapters on printing characters on the screen and an update on advanced features on the Spectrum. There the differences end.
The examples in the text, which usually consist of whole chapters, are the same as in the ZX-81 version. They include a graffiti program which displays the Spectrum character set and three chapters which show how a game of draughts is put together.
One useful part is a long chapter which provides a dictionary of all the instructions you can give to the Z-80 processor. It turns the book into a useful reference guide which should be of use to all beginners. It will, however, be of little use to advanced programmers - unless they want to brush-up on their terms.
The book is well-produced and you should have few problems with typing-in most of the examples. One small criticism is that a Sinclair ZX printer is used to produce an assembly language listing. All other listings are typeset and that listing sticks out like a sore thumb, as well as being difficult to read in some places.
The book also contains some useful appendices which give tables of conversions between hexadecimal and decimal and also a list of symptoms variables which can be used either in machine code or in Basic programs. Mastering Machine Code on Your ZX Spectrum costs £5.95.