Review: This is _the_ manual you need if you use IDA Pro for fun or profit. It covers a wide range of information ranging from disassembly basics to writing plugins for IDA. It provides sufficient detail without the tedious extraneous information you often have to dig through in technical books.
IDA is one of those tools that you can use for a long time and still miss a lot of the functionality that it has. Chris does a masterful job of illuminating these features (as well as the pieces everyone uses) with good examples and an appropriate level of detail.
There is a very well done map to this book in the "Introduction" before chapter one - this enables readers of any level of experience to focus. But, I found that there was value to reading all of the sections anyway.
The accompanying website is well done and provides the examples, a small errata and additional references. (http://idabook.com)
This may go without saying, but you should have access to IDA PRO to get the full value from this book. This edition is less applicable to the freeware version than the last edition was (although I'd still probably recommend it for anyone using IDA).
Bottom line: If you use (or plan to use) IDA PRO - buy this book.
Disclosure: I was provided with a free PDF copy of this book by O'Reilly as a part of their "Blogger Review Program" program. (http://www.oreillynet.com/oreilly/bloggers/)