101 Puzzles To Solve On Your Microcomputer is the best-produced of this trio. It has the largest format of the three - A4 size - and each question is accompanied by a cartoon. A nice touch is the spiral binding, which enables the reader to leave the book lying open while constructing a program to solve the problem. If I have a criticism, it is that the author has found it difficult to make all his puzzles original: he ingeniously sidesteps this point by dedicating the book to Lloyd and Dudeney, the most creative people ever to construct puzzles. And, it must be admitted, coming up with 101 new ideas would stretch the ingenuity of most people.

It's no coincidence that the famous problem about the five castaways, the monkey and the coconuts - an ideal problem for a computer - appears both in Clessa's book and in this one. Still, they're in good company. Last summer, The Sunday Times' Brainteaser, normally rather an original source of intellectural stimulation, used it.

Andrew Hilton has done a good job in sorting his puzzles into number-crunchers, problems involving the use of nine or ten different digits once only, exercises in probability and codes and ciphers. His book probably represents the best value for money of all three.