I read this book about 3 years ago about a thief.
Here's what I can remember about it:
He was in the middle of sneaking away after he stole something when a person called The Monk appeared to him and tried to convince him to come with him, but he snuck away while he wasn't looking. The Monk appeared to him again when he was giving the stolen thing to his client and tried to force him to come with him but somehow he got away then the Monk appeared to him a 3rd time in his bedroom and shot him. He wakes up to find he's in heaven and was going to go to hell because he stole things but two angels named Michael and Gabriel saved him from going to hell because they needed him to find a book some demons in hell stole, they present him with a choice for a companion a scrawny boy called Angelo or Michael (by this point the boy doesn't like Michael) so he picks Angelo to go with him and they end up in Valhalla where Angelo annoys Odin and they get into a fight where Angelo turns into a dragon demon. As they fight, the Valkyrie who served them drinks helps them escape, then all 3 of them fall into a pit where nothing dies.
Closer to the end They find out that Angelo is half demon half angel and that his grandfather who hears voices in his head is God.
I can only remember bits and pieces after that but it was a very funny book and I found it in a library in England.
Can anybody help me find this book?