I just finished putting the first shelf plus some scattered odds & ends into Shelfari, and I'm at 134 tomes. I had some empty space so I started a "books to read or re-read" shelf.
There were a few books that I didn't bother adding to Shelfari; they are too uninteresting and I need to get rid of them.
I went through the whole thing so far and added ratings to everthing that I've read. Three stars means "liked it." Less than 3 are degrees of not liking it, more than 3 are further degrees of liking it.
There are very few books I've read that I can say I really didn't like. I consider most books a learning experience, even if they aren't very good reading. That said, there are even a very few that I've thrown into the garbage, lest someone else accidentally waste a few precious hours of their lives reading it.