College Board, What's Good?

The great D. J. Smith once asked, "what is literary merit, anyway?" and of course I wanted to promptly reply with a typical Mariah answer, you know sarcastic with a hint of seriousness, but I didn't. I too wanted to know what literary merit is. Why are all of these books worthy of being mentioned for all eternity? Why is Their Eyes Were Watching God, one of the worst books I have ever read, considered a work of literary merit?
I feel like the term "literary merit" is like this award bestowed upon those who are memorable or make a difference, kind of like a noble prize, but not as prestigious. But there are a lot of books that are both memorable and make a difference, but they aren't considered a work of literary merit. Well, yeah, but there's a difference. Works of literary merit have this thing about them that makes them eternal. They have this flame that will never go out. Books that are just memorable or just make a difference only have a spark of what works of literary merit have.
I recently read Go Set A Watchman by Harper Lee and I must admit, I was disappointed. Maybe it was because I thought Lee was going to create another To Kill Mockingbird or it was simply just not good. Based on that, I wouldn't say it is a work of literary merit. It is only memorable because it wasn't as good as expected. I understand that it was a rejected draft, but still. Lee could have done so much better. It was obviously rejected for a reason. I don't think it was that well written and the content wasn't too great either. It's not awful, but being a fan of Mockingbird, I expected more.  
You know what novels are of literary merit though? The Twilight Saga. Oh my sweet Lord, those books are perfect. College Board needs to include them in the AP Exam. Nay, they should create an entire AP course based on The Twilight Sags. I'd get an A+ every term and a 5 on the exam. I'm going to write a letter.