I recommend books by the great Polish hard s-f writer Stanisław Lem.
"His Master's Voice" is a novel about scientists who receive the message from extraterrestrial civilization and try to decipher it. The narrator of the story is a mathematician named Peter Hogarth.
Another great book by Lem in which you can find a lot of reference to mathematics is "The Cyberiad", a series of short, humorous stories about adventures of two constructors, Trurl and Klapaucius. "The dragons of probability" is a masterpiece!
You can find out more about Lem's books here: http://english.lem.pl/