While I can agree with most of what you say, I believe that a system based on what shockme suggests would provide useful information, especially when coupled with PM reviews.

But we all know that the only reason to pay attention to these numbers is if we know that our tastes are similar to the reviewers.

Well, that's the point. I would sooner get see a rating by members of the PM community than those listed at a Bookstore or website.

I like to use all available resources when choosing a book, but sometimes I might not be particularly well versed on a given subject. Seeing several ratings may give provide the impetus to question why one book has a better approval rating than another. Answers to that question may or may not convince me to buy it. I certainly wouldn't stop reading reviews or asking other people (whose opinions I respect) what they think of a book. Anyone silly enough to buy a book based purely on a numeric rating is likely to make a poor decision anyway.

Of course the system won't be perfect, but then I wouldn't really say that PM is perfect either, although it provides a wonderful resource.

--Jim