Hybrid by Vanessa Wester

This is a book of two very different halves.  The first half is Caitlin's story.  She starts at college and meets a guy Steven.  They start off as friends, but it soon develops.

But Steven has a past he doesn't know about.  And when Steven finds out about it, it's too late for him and Caitlin.  The second half of the book is him finding out what he really is.

I enjoyed this story, although it seemed like two separate stories.  Southampton was a long long way from the Brazilian rainforest.  

http://www.amazon.co.uk/dp/B0081EV8Z8/?tag=jookuf-21