You might want to read the rest of his bio. up the page from the little bit you clipped there, and remember, that's from Wikipedia, not Encyclopedia Britanica...

I'm not sure he stole his entire life and all his material from Bill Hicks. It sounds like he actually did some stuff of his own.

I don't know Denis personally, but I like his stuff, wether he stole it from Hicks or not. I'm pretty sure Hicks was dead and not able to write the book for him though.