The Penguin Dictionary of Curious and Interesting Geometry

"For my final choice I must return to geometry, and this kaleidoscopic and superbly illustrated collection by David Wells. There are about 250 short items, and for me, at least, it is the more oddball ones that really leap off the page. It was here, for instance, that I first came across Malfatti’s problem. This is a conjecture dating from 1803 about the densest way to pack three non-overlapping circles into a triangle, and it took over 100 years for someone to realise that the conjecture itself was completely and utterly wrong. Above all, perhaps, David Wells’s book is great for dipping into, almost at random, with a nice cup of cocoa on a cold winter’s night."