The most gripping book I've read so far on my two week holiday is Marcus du Sautoy's Music of the Primes. These types of books are destined to be described as a 'fascinating journey'. It was, how shall I put it? A fascinating journey through the drama and personalities of the search for an explanation of prime numbers.
One of the sad things about it all is that there's a belief among mathematicians that your mathematical abilities decline after you're 30. Kind of depressing. Having said that, Euler and Erdos were apparently mathematically active to a ripe old age.