TITLE: Favorite popular math book
QUESTION [86 upvotes]: Christmas is almost here, so imagine you want to buy a good popular math book for your aunt (or whoever you want). Which book would you buy or recommend?
It would be nice if you could answer in the following way:
Title: The Poincaré Conjecture: In Search of the Shape of the Universe
Author: Donal O'Shea 
Short description: The history of the Poincaré Conjecture.
(Perhaps something like "difficulty level": + (no prior knowledge of math, as the book mentioned above), ++ (some prior knowledge of math is helpful), +++ (Roger Penrose: Road to Reality (?))
I hope this is appropriate for MO, since I think is of interest to mathematicians (at least for those who want to buy a popular math book for some aunt :-) ).

REPLY [2 votes]: Title: Prisoner's Dilemma 
Author: William Poundstone
Short description (from New York Times Book Review): The real originality of PRISONER'S DILEMMA lies in its colorful synthesis of logical material and historical and biographical narration [which] takes us in parallel lines through cold war history, strategic games of the nuclear age and the life of von Neumann . . . Lively, open and multifaceted.
Indeed, the book can be read as a whole or just by following one of those "parallel lines". Depending of the line you choose, the level of difficulty would be + or ++!