I just finished reading his book the Grand Design. It has a lot to do with explaining how the universe exists without the need for a deity and it also talks about how and why we came to invent religions and why they are no longer needed to explain the ways of the universe.

He is an atheist. Unlike Carl Sagan, who gets a hell of a lot more attention here.

EDIT: So it looks like I'm receiving quite a few downvotes. Not sure why to be honest. I meant no disrespect to Sagan, but it is true though that he gets heaps of attention here despite never being a spokesperson for atheism. From what I can gather, he seems to have been an agnostic deist. If that is incorrect, please prove me wrong and show me evidence to the contrary. Hawking is an atheist! Not only that, but his most recent published book is centred around the idea that the universe can exist without a god. It makes no sense to question Hawking's place in /r/atheism without also questioning Sagan's. Not that I have a problem with Sagan related posts at all. I realise he has helped lead a lot of people to atheism, which is fantastic! Downvote if you wish, but please don't interpret my post as anti-Sagan because it simply is not.