The Salesforce Handbook is now available on Amazon.com (finally)! Here's the link to the book. We would love it if some people could add some reviews. That would be really #superfrickinawesome!.
You can still purchase the print and PDF versions of the book at Lulu.com which are a bit cheaper. I guess the Amazon.com premium is for being able to find the book easier.
Wes is working on the Kindle version of the book now so hopefully that will be available shortly.