Invaluable by Dave Crenshaw, who also wrote the book The Myth of Multi-tasking. At first, I thought the book was kind of light. Like Critical Chain, it's told as a story with characters learning as they go. I realized after I was about half way through the book what I was looking for. Unlike something like Drive by Daniel Pink (another favorite of mine), this book doesn't go into a lot of theory. It gets right into some practical steps to help you become more valuable in your work.
For example, Jason, the main character, develops a chart of his activities and identifies those that are his strengths and areas where he would be hard to replace. The full exercise is available in the appendix for the reader to go through. The book continues to provide exercises to help the reader focus in on how they can make themselves invaluable at work.
So if you're looking for a book with a lot of theory that you can use to impress your client or discuss over drinks, this isn't the book for you. However, if you are looking for some straight forward exercises to help you be a more valuable contributor at work, I recommend it.