It's not very original (anybody remembers 9œ Weeks? probably not the intended public for this book, who weren't even born).
The sex scenes are a little unbelievable (not impossible, but certainly not coherent with the character's tastes and experience).
The female character passes for a smart-shy-clumsy-beauty-is-inside girl, and graduates in Literature but doesn't know or ever has listened to the Flower Duet in Lakmé (when this music appears in at least 5 Hollywood films that I've seen), nor La Traviatta... It seems the only book she has ever read is Tess of de d'Urbervilles. And she reads it over and over. I didn't know you can graduate in English Literature in USA by picking a novel and learning it by heart.
Then the guy is completely absurd. Like they have pointed already, by 26 is a billionaire (maybe he graduated in college by reading Wuthering Heights, and as he's smarter, it took half the usual time for him), and very acomplished, too. And his dark side is he's a great lover with kinky issues...
Not a smart reading. I give it a three for the same reason I like Pretty Woman or Flashdance... I really enjoy modern fairy tales, even the stupid ones.