The book represents Daniel, a kid who lives a life governed by his OCD (Hence the title). I really enjoyed it, partially because in some parts I could really relate to Daniel. Sara, a character in the book, brings Daniel on a journey in which he learns that what he experiences is a disorder. I would hate to spoil the story, but as far as I can say, I really enjoyed it and most likely so will you.
(Yes, it's one of those books that makes you feel empty after you finish it.)