The American Library Association awards a number of citations to notable books for young adult readers (Librarians usually class 12 yo as YA for review purposes: the category covers grades 7-12, but kids who like to read tend to skew a bit older.) There are also awards for notable books for young readers.
You can find the award lists here:
http://www.ala.org/Template.cfm?Section=bookmediaawards
For what you're looking for, you'll probably want to try the Popular Paperbacks for Young Adults lists. If you want to aim a little younger and for literature in the true sense, I suggest looking at the "Older readers" section of the Notable Books for Young Readers list. One of the best things to do is to copy a likely list or two, then take them to a bookstore and judge the books for yourself. (I'd suggest a library, but these titles tend to be very popular, and probably won't be on the shelves.)
A note about content, since someone brought it up: "traditional YA literature" usually has a coming-of-age plotline -- the best known classic American YA novel is
Catcher in the Rye. The subject matter in most of these books tends to be somewhat controversial and may well offend the conservative reader. Tough topics like drinking, drug use, child abuse, domestic violence, and especially sexuality come up often. They also tend to be rather painful for adults to read because they remind us of difficult periods in our lives that we would rather forget, but YA readers love those novels because they help them feel that they are not alone, and that their problems and worries are not so bad after all. Most YA paperback series novels are what might be termed "YA lite" -- they tend to soft-pedal the soul-searching and push the romance (or in the case of those meant for boys, the sports.)
