Absolutely. If I've understood the article correctly, I can refer to my books even when I'm out of the office? This is brilliant, I wish I'd known about it sooner.
One thing I don't quite follow: it's easy to find out the ISBN number of a book you don't own on amazon or so, which would allow you to add arbitrary books. I don't see how they get away with that.
The access they provide is nothing beyond what you would get doing a normal Google book search. It just allows you to search over aggregations of books which you may or may not own.
I would love to be able to prove ownership and get full access to the book/override the limited preview.
I put in the ICBM of Founders at Work, but Google only permits its limited preview. My plan was to take the book to my college dorm when I move in late this summer, but I guess I will do without Chapter 19 and Chapter 28.