What's the name of that book /s

[Tracy]

So I remember reading this book last year 2012, I assume its for teens since I found it at my high school library. I know it's a series since there was suppose to be a sequel coming out and it's a pretty new series I think. I remember the book had a green cover and I want to say the title started with an A??? I'm pretty sure it had a butterfly on it...
The book was about this guy who is looking for his girlfriend that just disappeared and he finds out that these people that kidnap girls are looking for her too. He has 2 friends that help him. One is a weird kid who's the son of a janitor, and the other is a girl who gets picked on and has lots of tattoos.
*spoiler warning!*
He saves his girlfriend and other girls from this strip club type thing.
At the end he meets this nazi survivor who says she is trying to save people from this nazi commander she used to know that is still alive.

I actually found it! its called Shelter by Harlan Coben

[Tab]

were there any supernatural/paranormal elements in the story?

[Tracy]

nothing really supernatural or paranormal that I remember.