That's strange, there's so many sites like metacritic, reddit, and even slashdot that allow people to rate the content they view/read. Too bad this can't be applied to books.
And notice that despite hundreds of thousands of self-published books, it's not occurring now... Ever considered asking why?
Almost nobody is willing to spend 100-200 hours to find a single book worth reviewing. And, sadly, the very few people who might be willing to do so on an occasional basis are completely eclipsed by desperate authors who have friends "review" or purchase reviews or whatever.. (Not that they are necessarily common, but given how few reviews occur, even 1 in 100 authors means false reviews will eclipse real reviews 10 to 1.)
Closing your eyes and pretending that magic Internet pixies will happily do unpleasant work for free isn't working now. Why should it start working in the future?
(And if you are wondering why it works for music, the answer (1) the investment by the reader/listener is vastly smaller for music - I can listen to music for 3 minutes and decide if I like a piece, as opposed to 2-3 hours for a book and (2) much of the discovery occurs in venues where someone else is doing the filtering for the audience. Open mike nights with no filtering are marginal now. Imagine how they'd do if they featured a single unknown band playing for 2 hours... How many would be willing to sit for weeks to hear one band that was actually decent? (And remember, no talking with friends while listening. This music requires your undivided attention.)
Welcome to the challenges of self-publishing. Sadly, there's no magic here.