The other two books from Interface form a series. Spectrum Machine Code Made Easy, Volume One is for the beginner. It is easy to follow and starts, as with most other machine code books, with an introduction to binary and hexadecimal number systems.
The layout of the beginners' book seems to have been thought through carefully, as each chapter deals with one of the major aspects of machine code and, unlike some other books on the market, does not disconcert the reader by moving into another realm halfway through a chapter.
Most of the aspects of machine code covered in Baker's book are included but this is better as it is easier to read and the layout of text and illustrative examples is better.
The one criticism is that the listings, like Baker's, are sometimes set in type and sometimes listed on the Sinclair printer.
The companion volume is Spectrum Machine Code Made Easy, Volume Two. It is for the advanced programmer and takes it for granted that you have some knowledge of machine code. Because of the complexity of jumps, both relative and absolute, in programs and the specialised logical operations, there are separate chapters on those subjects.
That is as far as the book goes along conventional lines, however, as the author, Paul Holmes, explains the use of ports and interrupt modes. They are two subjects which are rarely mentioned in books of this kind.
The ports are dealt with in Basic and machine code and some interesting effects are obtained with sound and colour on the Spectrum.
No previous pure machine code book has dealt with interrupts in the Z-80 system. This one explains the subject easily and competently. The chapter on interrupts justifies what is anyway a good book on machine code and even if you do not buy volume one, which is also excellent, is well worth £5.95, which is the price of each volume.