I was interested in finding out what grade level the books are that my dd is reading and a friend sent me this site:
It's very easy to use. You don't have to log in or anything. Just choose the bubble for "parent," type in the book you are curious about, and the site will reveal information about that book, including interest level (IL) and book level (BL). Click the little question mark by each abbreviation for an explanation, but here's the quick version: if the BL says 2.4, that means the book can typically be independently read by a second grader in the fourth month of the school year.