I read the first edition of this book as an undergraduate student of mathematics and, like many of my peers, was astonished at the effortless way in which an entire new class of numbers was defined, and then extended again to embrace the world of mathematical games. It's deep, yet playful (anything which deals with 'surreal numbers' is OK by me) and accessible, although not to someone without some knowledge of algebra. Conway is an inventive genius and nowhere is that more obvious than in this book.

This ranks with "Mathematics made difficult" and most of Martin Gardner's mathematical diversions as essential reading for enthusiasts of mathematics. It reminds you why it's fun. ( )