I have Darrell's D700 book and have not yet bought his D800 book. I will when it's available on Kindle. I am not so sure how much I will use it however, except to say that it is simpler then Tom's so may be a good ready reference.
Tom's book is a really valuable reference, not only about the camera controls etc, but the in depth descriptions and discussions of just about every aspect of the cameras minute details. From how to fine tune to what are the best memory cards, this is a real gem and I learned so much.
If however you want an easy reference written in plain English and a major step up from Nikon's poor manual, then buy this one. It will be well written if the D700/D7000 manuals are a measure, but the depth of Thom's book is not there in my view.
In short if you want a manual that tells you both how the camera works and how to get the very best out of it, then it's Thom's for me. Alternatively, splash out on both references