Sit'n'Go Pro by Johnny Rothman

As the title suggests, this is a book dealing solely with online sit'n'go single table tournaments. These are games played with between 5 and 10 players where the top 3 finishers take money. These are a great way to steadily build a bankroll as it can be easy to finish in the money.
Johnny Rothman's book is a great instructional tool from a well known sit'n'go expert who has amassed over $100000 from playing in these single table games. If you check out his site you can see screenshots of some of his accounts. It will blow your mind.
The book is only available online, so you know that it won't be advice that other players are using, unlike some of the more famous paper books.

The best bit of the book is that it is easy to read for beginners and it has a good learning curve, so even if you are an intermediate player you will definitly learn some useful tips.

For more information about this book you can check out the authors website, here.