I really like Scott Sigler. He writes some awesome alien books, let me tell you, and the Infected series is awesome.
However, it is not for the feint of heart. Sigler... as much as I like the man and his writing, I kind of feel like he's gross for the sake of being gross sometimes. Sometimes not, and I will conceded that there is a point to the gross in the first one. Our main character, Perry Dawsey, basically has an inferiority complex and feels that he can't show any weakness ever, so he doesn't do things like go to the doctor when little blue triangles show up on his skin and start talking to him.
Instead he rips them out of his own body by doing things like like burning his own arm on his stove. You heard me. He slams his arm down on a scalding hot stove burner, then grabs the head of the alien and RIPS it out of his body (by the way, this aliens embed themselves into your body and use hooks to stay there. And he just ripped it out.)
The story line is amazing, and the concept great, but you really can not read this if you don't do well with gross things, and even if you do, I wouldn't recommend reading it on your lunch break.
When I tried to think of a "gross" book that I like, the first thing I thought of is that I love a good gory scene. So I redefined "gross book" to "gory book" in my head and had a lot of books to pick from. As we've discussed before, I had a pretty decent Stephen King phase (and there's all sorts of gore in Desperation, The Regulators, The Long Walk... the list goes on) plus there's quite a bit of gore in some of my favorite YA books like Ashes and parts of Unwind, and books like World War Z and I Am Legend. But I had to go with The Running Man for one simple reason. Have you ever thought about what it would feel like to hold your own intestines in your hands? Neither had I, until I read this book. And say whatever you want about Stephen King and his writing, but the scene I'm talking about is incredible. It's desperate, it's heart-breaking, and it's sick... and I love it.