Friday Why: What makes books absorbing vs. good?

I started thinking about this because I recently read Libba Bray’s THE SWEET FAR THING, and THE EARTH, MY BUTT, AND OTHER BIG ROUND THINGS by Carolyn Mackler. And my reaction to both was that they were not very good…but they were extremely absorbing. The kind of reading where I totally get lost in a book and forget what’s going on around me, and where I don’t want to put it down. But they weren’t very good. It seems contradictory, but that’s my reaction, and as I think about it there are a fair number of Teen books that I feel that way about, whereas absorbing and good almost always go hand in hand for me with both younger kids’ books and adult books.  So why?  What is the distinction between what makes a book good and what makes it absorbing?  And why do Teen books seem to lend themselves to being absorbing-but-not-good?