I'm reading "An Utterly Impartial History of Britain" by John O'Farrell, and enjoying it vey much. It's a thorough history with lots of random one-liners thrown in.
My favourite parts so far are Emperor Hadrian buildng his wall ending at Wallsend ("a sensible place to aim for"), in order to prevent the Picts coming over and calling him "Adrian" to wind him up, and Queen Boadicea rebelling over the incorrect spelling of her name.