Recently, I received a review copy of the book, "The LEGO MINDSTORMS NXT Idea Book" by Martijn Boogaarts. I'm definitely an avid Mindstorms user, so I'm always looking for good books. My sons and I are always playing with our set, I started a robotics club at my younger son's elementary, and I co-coach a junior high FIRST LEGO League team. Finding great projects is a good way to supplement the creative homebrew creations. The included instructions are great for ideas, but you want more after some time.
I really enjoyed this book. The layout is well-done with a good number of projects. There are a huge number of pages dedicated to showing how the pieces go together. Instead of just padding their page count tough, they did a good job of reducing the number of these pages far below the typical one-step-per-page Lego uses in their booklets. The write-ups were good, the instructions were clear, and most importantly, the models were fun. For the most part, they also played nicely with one standard set. Too many books tantalize you with neat looking pictures, but then you realize that you need two brains, additional blocks, etc. Not that none of these needed extras, but it wasn't the norm anyway.
If you are having fun with Mindstorms NXT but are running out of ideas, I highly recommend this book. I would have considered it worth the money even I had paid for it!