There is no doubt that this is a clever book, as I have grown to expect from John Green. And I think Hassan might possibly be the best side kick in the history of YA fiction. An Abundance of Katherines is definitely not as mature as The Fault in Our Stars, but it still has a certain depth that will be best appreciated by mature teen readers. 
 There are some minor swear words, and an abundance of the word "Fug"being used in exchange for the F-bomb. (Unfortunately, the explanation for why isn't given until far into the book, long past the point where I had given up looking for one.) In the end, I was really happy with the balance of serious and light. Great book. Don't change a thing. 
 A quick note on anagrams: they are the best thing since sliced bread. BUT their presence in the book felt a bit... gimmicky. I'm sure Colin's character was all the better for it (because, let's be honest, whose life isn't better with anagrams, am I right?)