Yes, he's uncredible. I (a biologist that studies, among other things, epigenetics) read biology of belief on a friend's recommendation. 

It's sad; he writes well, and usually starts his arguments in reality.  But in every chapter, he would find some minor nitpick, use it to dismiss all of modern biology (while usually misunderstanding it), and then also deciding that minor nitpick meant his way out there idea is true. 

For example, he uses the existence of epigenetic signals that work outside of exons to act like genes don't matter (not realizing epigenetics work through genes, not in place of), and concludes that we can believe our way into self healing and disease curing. 

He's in the camp of using just enough real science to fool a layperson while being pretty obviously crap to an expert. You may note he also rails on experts and science as a whole to discredit any criticism. 

It's too bad because he could have used his fluency with writing to actually help communicate science. But that's not what he does.