I would go with "Proofs and Refutations: The Logic of Mathematical" by Lakatos, its a dialog-form history of defining Euler's formula and it shows the human side of mathematics as a science. I think its great as math has this unique status as providing with undoubtable knowledge but history shows that human error is possible even in this field.

Alternately "The Unreality of Time" by McTaggart, it has less than 20 pages and argues that time doesn't exist since it is logically incoherent.

Not sure if this would get someone hooked up but for me those two were extremely fun reads.

EDIT: Just to be clear – both are meant as philosophy books, even if they touch on other things. :)