Anansi Boys by Neil Gaiman

Fat Charlie Nancy is not actually fat. He was fat once but he is definitely not fat now. No, right now Fat Charlie Nancy is angry, confused and more than a little scared - right now his life is spinning out of control, and it is all his dad's fault.

If his rotter of an estranged father hadn't dropped dead at a karaoke night, Charlie would still be blissfully unaware that his dad was Anansi the spider god. He would have no idea that he has a brother called Spider, who is also a god. And there would be no chance that said brother would be trying to take over his life, flat and fiancée, or, to make matters worse, be doing a much better job of it than him.

Desperate to reclaim his life, Charlie enlists the help of four more-than-slightly eccentric old ladies and their unique brand of voodoo - and between them they unleash a bitter and twisted force to get rid of Spider. But as darkness descends and badness begins is Fat Charlie Nancy going to get his life back in one piece or is he about to enter a whole netherworld of pain?