[Nyx]

I enjoy the Anime and Manga for the boobs part, but the story was really good and had potential so I picked up the light novel, and found that it became serious and wasn't for the penis as much as a good read. If you want something more serious and enjoyable pick the light novel up at Baka-Tsuki, great read imho.

Forgot the mention that it is MUCH farther in the story than the Anime and Manga. They have already fought Dragons in it! xD