Ian Stewart 
Cows in the Maze [PDF ebook] 
And other mathematical explorations

From the mathematics of mazes, to cones with a twist, and the amazing sphericon – and how to make one – Ian Stewart is back with more mathematical stories and puzzles that are as quirky as they are fascinating, and each from the cutting edge of the world of mathematics. We find out about the mathematics of time travel, explore the shape of teardrops (which are not tear-drop shaped, but something much, much more strange!), dance with dodecahedra, and play the game of Hex, amongst many more strange and delightful mathematical diversions.