My favorite Math-related books geared towards undergraduate students:
Flatland: A Romance of Many Dimensions - Edwin A. Abbott
The Non-Euclidean Revolution - Richard J. Trudeau
99 Variations on a Proof - Philip Ording
Math Girls - Hiroshi Yuki
The Shape of Space - Jeffrey R. Weeks
Weapons of Math Destruction - Cathy O'Neil
An Imaginary Tale: The Story of √-1 - Paul Nahin
Visual Complex Analysis - Tristan Needham
Visual Group Theory - Nathan Carter
Zombies and Calculus - Colin Adams