[cvcount]

Just wanted to call out a couple of moments where this manual is far better than it needs to be, considering the target audience.

(from page 130) a description of calculating how long your ZX Spectrum has been powered on includes a discussion of the problem of a race condition when the counter ticks over

(from page 117) a program illustrating that the RND function uses a pseudo-random number generator

[TheOtherHobbes]

It's an exceptionally good manual, for many different reasons.