Why AP?

At first, I was a little surprised that this was an AP-level novel.  It does not seem like a very challenging read when it comes to diction, sentence structure/style, motifs, allusions, etc.  The writing itself seems less complex than that of the other AP-level novels I've read.  However, I think what makes the story AP-level is its meaningfulness.  The story is pretty much a book within a book and it is more about the character's lives than anything else.  It's unique because its characters (who have their own backgrounds and their own points of view) are connected by the story that Leo wrote called The History of Love.  I think the story's complexity lies in all of its underlying meanings, which give it literary merit.