## Reviews

Of all the classical functions, the Gamma function still retains much of its mystery and intrigue, since Euler first spotted it as something "worthy of serious consideration". In Gamma, Julian Havil explores Gamma from its birth and in so doing simultaneously deals with many related functions, problems and issues that go beyond the conventional territory of functions alone.
The Code Book on CD-ROM, by author Simon Singh and designer Nick Mee, is the interactive version of the best-selling book of the same title. Singh has already shown in The Code Book and Fermat's Last Theorem that he is an excellent communicator, able to explain complex ideas without using obscure jargon. But while the main achievement of The Code Book is to make codes and ciphers intelligible to everybody, the CD goes further and allows you to become a code builder and code breaker yourself. You will find yourself first turning into a code builder, fearful of being cracked, and then into a dedicated code breaker, following tips on how to crack the ciphers.
It seems amazing that the universe could be characterised by a mere six numbers, yet, according to Astronomer Royal Martin Rees, this is the case. He makes an excellent case for the necessity of these numbers, though he does not show that they are the only numbers we need.
Early in our mathematical careers, we are introduced to prime numbers. These special integers, which possess no divisors other than themselves and 1, are the building blocks for all the integers. Thus an understanding of the properties of primes, including where to find them, is an essential part of number theory, and any serious discussion of prime numbers will inevitably lead to what is arguably mathematics' greatest unsolved problem: The Riemann Hypothesis.
Bill Bryson - he's a travel writer isn't he? He goes places and writes about them, tells amusing anecdotes about things he sees and people he meets, making his readers laugh at the same time as teaching them something about the places he visits?
Many people, when they look back, can pinpoint the precise moment when their interest in mathematics was awakened - it was when they found a puzzle that intrigued them. Perhaps they now realise the puzzle was trivial or insignificant, but at the time something about it captured their imagination and started them on a path that may have led very far - perhaps even into fundamental mathematical research.
The Four Colour Theorem - the statement that four colours suffice to fill in any map so that neighbouring countries are always coloured differently - has had a long and controversial history. It was first conjectured 150 years ago, and finally (and infamously) proved in 1976 with much of the work done by a computer. The published proof relied on checking 1432 special cases, which took more than 1,000 hours of computer time.
Geometric dissection is the mathematical art of cutting figures into pieces that can be rearranged to form other figures, preferably using as few pieces as possible. You may already have come across puzzles such as the Aviary Tangram, the pieces of which can be used to form an egg, a chicken and many other shapes; but the ingenuity of the dissections shown here may still be a revelation to you, as they were to this reviewer.