5 stars - the best books I've ever read. Only 20 spots available (although I think I need to update the number to 5% of all read books).

4 stars - very good books, enjoyed them, will probably read them again sometime.

3 stars - ok books. Nothing that particularly marks them as good or bad.

2 stars - finished it. There are some problems with it, but nothing that completely breaks them.

1 star - didn't finish, or finished out of spite. Hate it, important problems that break the book.