Google Books API - Getting Book Ratings?

I cannot find a way to get a Book's Ratings through the Books API provided by Google.

All I figured out is how开发者_运维问答 to obtain search listings, which do not include ratings and description.

Help would be very much appreciated.

I've never used Google Book API, but its documentation claims you can only retrieve an annotation (incl. review) for a specific user.

Another proof is some post by Google employee who claims it's not supported (yet).