Sustainable Software Development brings together principles and practices for building software that is technically superior, delivers exceptional business value, and can evolve rapidly to reflect any change to your business or technical environment.
A lot of good information in this, if you're looking to get into Agile development. Overall, I found this book to be a bit too full of what felt like "marketing" almost for Agile/XP mythologies and practices. There were a few parts of it I got something out of, though, so it wasn't too bad.