Typo. There are 10 books in circulation. I actually enjoyed the films as well. I really wanted to see the first storyarc end, which consists of the first five novels. I just that Lerman is wrong, considering he's just a noobie teenaged actor. I might believe him if he was the director, but I don't put any weight on his comments. He doesn't speak for the studio.
I also discovered that 20th Century Fox had previously greenlit the third film for release in 2015, as indicated by this link:
http://camphalfblood.wikia.com/wiki/...m_franchise%29
From what the links says, that the principle cast, Logan Lerman, Alexandra Daddario, Brandon T. Jackson, and Jake Abel are all signed on for three films. I'm wondering if this is just Lerman's attempt to get out of his contract for the third film.