I participated in several beta and early access testing of products, reviewed books but never participated in an Early Access Program for a book. And certainly Manning Early Access Program sounds interesting.
An early release version of my book EJB 3 Action is now available at http://manning.com/panda/
It's a little better form of pre-ordering from Amazon or a publisher web site. You immediately get access to the source or final pre-production version of the book online and Manning Publications will ship you a book as soon as book is published. In the mean time you are the beta testers of the book (:
I will appreciate you participate in this program, pre-order a copy and help find any errors in the book (: