For book #11, I read the last John Green novel I hadn't read yet, which I borrowed from a friend.
Katherines, like all John Green books, was a pretty quick read. I read it in one sitting. I wasn't super impressed. Like, it was a John Green book, so it was good and I liked it. But it's definitely the least enjoyable of all his books. It was cute and it was funny, but it didn't yield the emotional connection that Looking for Alaska or The Fault in Our Stars or even Paper Towns did.
So now that I've read all of his books, I can rank them from best to least good (I don't like to say "worst" in this case because that seems to imply that John Green has bad novels).
1) The Fault in Our Stars. By far!
2) Looking for Alaska
3) Paper Towns
4) An Abundance of Katherines
5) If you can count this one because it was only half written by John: Will Grayson, Will Grayson