My favourite in-depth analytics book. Admittedly the only other one I've read is the one by Avinash Kaushik, but I find this much more useful simply as it focuses on Google Analytics, rather than talking about other analytics packages.
This book clearly explains the basics, then goes into huge detail about certain aspects. It's very easy to skip the more complex sections if you wish, and the author explains that you won't be missing anything crucial if you do skip it.
One of the most useful sections is that it explains what metrics different types of websites should be looking for, for explain showing what an e-commerce site should be particularly focused on.
Yes there are lots of blog posts around the net explaining analytics, but I'd still recommend reading this for the expertise and advice contained.
The only downside, it is outdated in some places. Within a few weeks from writing this review (Mar-11) a redesign of GA is coming out, so some guides are likely not to work in the future.