atdgScott Herold just released chapter 4 from both books from the Advanced Technical Design Guide. He plans to post 2 chapters every 2 :weeks and at the end post the books as pdf for free:

Once we have all free chapters released, we’ll bundle the whole thing up in one nice PDF package so people can actually travel with all the info they will ever need on VI3.

It’s really nice that this book will be available for free, but by the time it is, we probably are all into the public release of vSphere 4! 😉