It's common to see competing titles published at about the same time, but even granted the fact that publishers are stampeding into the micro market at the moment, it's unusual for the same publisher to launch two competing books.

But Interface seems to have managed this puzzling feat. Toni Baker's book seems to be based loosely on the series of the same name published in ZX Computing, although clearly it provides much more detail. It reads well and manages to make the fine balance between plunging you into a subject too fast and keeping things too simple.

The two-volume Spectrum Machine Code Made Easy by Messrs Walsh and Holmes is - of course - longer, but perhaps not as much as might be thought. It does, however, show the odd sign of padding; there is repetition around the end of volume 1 and the beginning of volume 2.

One you hit volume 2, the information gets more bitty and non-systematic. The tables and appendices are useful, but could have been made more so if they were better releated to the text.

The advanced stages of Toni Baker's book, on the other hand, seem to progress more logically from the beginnings, and culminate in a fairly detailed draughts program, along with a few pointers to producing graphics.

Neither of the two 'courses' has an index, which is a pity, but both will nevertheless take you a fair way into machine code. It's difficult to choos between them but Mastering Machine Code probably has it by a nose.