I found AZ ratings to be mostly useless, what would be better is the total number HN/SO points accumulated from all the recommendations for that book.
edit: not a mix, but separate points for each community
Re:Show HN: HackerBooks.com
by thibaut_barrere on Tuesday February 22, 2011 @06:06AM
(#2249484)
Mmm - a kind of book karma. Something like mixing the karma of the commenter with the heatness of the discussion etc ?
I think being able to filter on SO vs HN would definitely give different results, too.
The topics are sometimes fairly different on both sites.
On AZ ratings: I wrote that down. It's somewhat complicated because Amazon just made it a bit harder to embed that. It now has to be an iframe; the iframe url must be refreshed every 24 hours.
But overall this should be doable to, I'll see if I can make it usable.
Thank you!