I think you are seriously underestimating the content most young teenagers are exposed to (has it really been so long?). A book being considered YA does not necessarily mean family-friendly, no-blood-and-guts G-rated. It has to do with the main characters being relatable to a younger audience as well as an easy-to-read writing style (as in, not a tome about quantum physics like Neal Stephenson's Anathem, which has nothing in the way of gore or sex but not something I would consider YA-appropriate). It is not the same as "childish" or any other derogatory label, and the mere presence of gore does not exclude a book from being appropriate for kids. I have not read the books, but my then-12-year-old sister read and enjoyed them, and she doesn't read anything (a horribly depressing fact to both me and our mother), which is proof enough to me that the books are YA-friendly.