If you are new to web analytics or need to brush up your skills, I recently read Web Analytics Demystified: A Marketer's Guide to Understanding How Your Web Site Affects Your Businessand found it very helpful for this category. If you are a little more advanced, you might try another book from the same author, Eric T. Peterson, Web Site Measurement Hacks.Perhaps what I like most about both of these books, is that Eric makes it simple. In addition, Eric has experience with web tags, which is particularly beneficial when your site is distributed across multiple systems.
Eric also has a companion site for his Web Analytics Demystified book. In addition to companion files to Web Analytics Demystified, he has done a lot of work to bring the web analytics community together. For example, Eric has organized Web Analytics Wednesday where professionals all over the world meet locally on the 2nd Wednesday of every month, at 6 pm, to discuss web analytics. I attend the local Web Analytics Wednesday in Portland, and met Eric himself, along with folks from Web Trends and Intel.
So if you need to get a better handle on web analytics, even if you are just starting out, give these books a shot and join the web analytics community.