I checked out your site. Where is a Lawyer when you need one.
Hey Gerry can you ask Marty??? [Our own personal Lawyer]

I looked at the "back of the book" stuff. My feeling is that those are intended to be quoted.
The back of any book is usually stuff written by a hack at the publishing house
OR by "authors" asked for quick reviews. This stuff is intended to sell the book.

What you are doing is within the spirit of what that stuff is intended to do.