The Police Riders handbook, is a handy small A5 size, perfect for carrying with you on the bike if going away. And what a great time to analyse your own riding when you get a few days of uninterrupted miles. There are many good biking books on the market, but I strongly recommend both these books as must reads.
The book is readily available from Amazon, or Fishpond here in New Zealand. Prices vary from place to place , so it pays to shop around for a copy.