It may, in fact, be unfair of me to review Project Cain before reading the companion novel because I get the feeling that much of what is really key to this series is in the other book. There's a sense in Project Cain that the young protagonist (Jeff), created from the DNA of a long-dead serial killer, has been through so much trauma, he's unable to actually talk about a lot of it. Thus, much of the intrigue and drama happens offstage (off page?). While this is effective and authentic to the character's point of view, it does leave the reader wanting, and I suppose what I'm actually "wanting" is the second book.
While this book has a clear sci-fi structure (bunch of kids are artificially/scientifically created from the DNA of famous serial killers; new take on the nature/nurture debate), it also has its roots in good old-fashioned horror. So if you don't like things that go bump in the night, don't read this book. Although having said that, there's really not too much actual gore on the page. A lot of it is implied but not rendered in detail. So folks who like horror but are nevertheless a bit squeamish, like me, should be able to cope with this narrative. No promises about the grown-up companion novel though.
The main character's voice is very authentic and easy to relate to. The book is told from the first person point of view in the voice of a cocky, but extremely anxious and scared (with good reason) young man who, in the first chapter, discovers that his whole life is a lie and he's really a scientific creation born of a horrible experiment. It's kind of a "buddy drama" in that he soon takes up with a mysterious black ops type agent and they go in search of answers. No girls or romance here. It's drama/action/horror all the way! I enjoyed the book and read it quickly but found portions of it repetitive. Jeff and his black ops bud (Castillo) spend a lot of time on the run and hanging out in seedy hotel rooms staring at computers and looking for answers. But that's the nature of the best in this story. So be prepared for it and you'll sit back and enjoy the narrative. I guess I need to go read Cain's Blood now to get the full picture ...