Sit 'n Go Strategy: Expert Advice for Beating One-Table Poker Tournaments by Collin Moshman is the first book to give a comprehensive look at every stage of sit-and-gos, or one table tournaments.
Single table tournaments are a much different type of poker than regular tournaments or cash games. In early stages players need to be tighter than normal, and in later stages players need to be much looser. This book emphasizes these concepts as well as others like chip equity vs. actual money equity, abusing certain situations when you're on the pay bubble, and mathematically unexploitable play.
Unlike in many other forms of poker, there is pretty much a proven way to play successfully with a "cookie cutter" strategy in single table tournaments. Recognizing all the situations and recalling what the best action is is the difficult part. To that extent, Moshman lays out a correct winning strategy for low to mid stakes single table tournaments.
This book is a very good start to anyone who wants to play single table tournaments. It will help you destroy live single table tournaments and satellites, and will get you started in beating low to mid-stakes online ones as well. Like many forms of poker though, single table tournaments can be mastered only through experience and training, so expect to read this many times as you get better. You will extract something new and useful with each read.