I was just wonderin if anyone had any particular recommendations, perhaps to start building a definitive reading list up.
Heres a few that I've read to start:
Fermats Last Theorum (Simon Singh) As in the name, more biographical than mathematical
Flatterland (Ian Stewart) Fantastic take on a 19th century book about different geometries, starts by explaining 4d by exploring the way our 3d world would look to a 2d or 1d person!
Chaos (James Gleick) Quite Physicsy, but a good read, yet again quite biographical, some have said that it gets hard work to read quite soon after opening!
Goedel, Escher, Bach (Douglas Hofstadter) is a good one, and has some very interesting parts about logic and some clever dialogues, but also a lot of rambling in the second half.
Music of the Primes(Marcus du Sautoy) was good, didn't have all that much mathematical content but it was fun to read.
What is Mathematics? (Courant and Robbins) reads a little bit textbook-ish-ly* (gah, who would think I spoke English? ), but definitely the best maths book I've ever read.
*Roughly translates as "like a textbook"
The Number Devil: A Mathematical Adventure (Hans Magnus Enzensberger)
Art of the Infinite (Kaplan) More mainstream, targeted at expanding mathematical awareness. Certainly a good read for those who have perhaps gained Mathmophobia!
Uncle Petros and Goldbach's Conjecture Light hearted look at the life of a mathematician. Reads like a novel, yet with the odd bit of mathematical content.
My Brain is Open: The Mathematical Journeys of Paul Erdos (Bruce Schecter) Yet another biographical book, but well worth the read! Not that much maths in it, but looks interesting
The Code Book (Simon Singh) Interesting exploration into the different types of codes and CYPHERS used throughout history. Is a very good GENERAL MATHS BOOK, covering elements of basic number theory, physics (potential of photon money!), statistics (frequency Analysis) and computing. I found it interesting but view it more as an encyclopedia for reference rather than a comprehensive account.
The Man who knew Infinity (Robert Kanigel) Book about Ramanujan, yet again more biographical, but still worth a look.
Infinity: The Quest to Think the Unthinkable (Brian Clegg) Am currently reading this. This is definitely one of the better books on the subject. A chronological biography of the concept of infinity, from Greeks to present day.
Feel free to add further books to this list, how about the From Here to Infinity (Ian Stewart), or The Man Who Loved Only Numbers: The Story of Paul Erdos and the Search for Mathematical Truth (Paul Hoffman) an alternative to The Man who knew infinity?