I don't think books should be age rated either.
Besides the fact that reading is a wonderful thing that should always be encouraged, it is vastly different from a film.
Films go back maybe a couple of centuries, books and literary works go back thousands of years! Who should start categorizing them? And where the hell should they start?
Books require reader interpretation, you need to comprehend the words and an imagination to put it into context. With a film, the direct audio and visuals impose that upon you.
A 5 year old may be able to read about a death in a novel (loosely) but they wouldn't have the comprehension to string the text together and form a conclusion on what it would look and sound like.
Also, books are fairly regulated by parents until a child can pretty much decide for themselves, by which age, there isn't gping to be a whole of difference between what they can read and what they can watch.
My dd has been a bookworm for as long as I can remember, she read The Hobbit at 7 years old, and may not have understood it completely, but got the main concepts. She is now 9 and I wouldn't dream of letting her watch the films.
From another practical point of view- how would you age rate a book? Solely on explicit language, or the obvious content? What about the metaphors and underlying themes? Some of the stuff my dd reads (by Jacqueline Wilson) has some very deep issues of child abuse, but until she is able to comprehend the more subtle themes, they won't affect her. Does this mean she should not be allowed to read it?
I am pro-books. Kids have enough distractions from reading as a pleasure these days, don't fix something that isn't broken and insert more obstacles.
In my opinion YABU to exect age ratings.