This is an extremely well-written book which is entertaining and easy to read. It's almost defining a new genre; rather than saying anything new to software practitioners, it reads like a popular science book. In a sense, this is like an episode of Horizon telling you why software is hard.
And fundamentally, this is what the book says; it says, despite the best intentions of all involved, software is hard. It says this at the start, it says it at the end, and it says it in the middle. If you're in the industry, you won't find any new revelations here; if you haven't done so already, go and read "The Mythical Man-Month" for the lowdown on exactly why it's so hard.
The book is written without finger-pointing, and that is its second greatest weakness. Scott Rosenberg decries how the software industry falls short of holding inquests into its failures, but then stops short of doing so himself. He hints that changing requirements are a Bad Thing, but doesn't challenge Chandler's design or technology choices, despite the fact that these are clearly contributing factors to the immense slippage.
Overall, entertaining, light and fluffy - just don't expect it to tell you anything you don't already know.