Ooh Jane,
I just love the way you put me in a spot.

But here's my 2 cents
I own Dan's book (among many other
SEO books) and what's different about my book is that it does not focus on theory.
You won't find very basic information that you can get from any free resource online - such as what metatags are and what the history and geography of search engines are (yes there are some books that actually go into that whether its relevant to the user or not - and they put me to sleep!!

).
I've used some very specialized techniques and content (niche reports or white papers) to draw traffic and create an "authority" site that the search engines love. I honed my techniques over two years and realise that they made my sites immune to all the updates and dances so that algo changes hardly even touched their rankings.
Again, I focus very little on theory in the book, and go straight to the nitty-gritty of my techniques covering them all in just 81 pages! No fluff, no filler.
I found Dan's book a bit repetitive and very basic, so if all you're looking for is to brush up on the basics, then its ok, though Sean Burn's "
Rankings Revealed" does that much better.
My book is for those already familiar with the basics, but loking for a way to keep their rankings through the algo changes and give their sites a competitive advantage.
More than two cents, but I hope it was worth your while.
Priya