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.

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Help would be very much appreciated.

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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).