If you have read any of David Wells' "Curious and Interesting..." books you'll know roughly what to expect. This is a great book for dipping into. I thought I knew lots about primes, but there's so much here to grab your interest. In addition to the formal stuff, there's lots of bits and bobs that are just there for amusement. I never knew that there was a definition for 'Sexy Numbers', but they are in here. Just like his other books, you'll find yourself dipping in frequently. Absolutely brilliant.