Terry Pratchett 
Small Gods 
(Discworld Novel 13)

 » You should do things because they »re right. Not because gods say so. They might say something different another time.  »
Religion is a competitive business in the Discworld. Everyone has their own opinion and their own gods, of every shape and size – all fighting for faith, followers, and a place at the top.
So when the great god Om accidentally manifests himself as a lowly tortoise, stripped of all divine power, it »s clear he »s become less important than he realised.
In such instances, you need an acolyte, and fast. Enter Brutha, the Chosen One – or at least the only One available. He wants peace, justice and love – but that »s hard to achieve in a world where religion means power, and corruption reigns supreme . . .
 »An intriguing satire on institutionalized religion corrupted by power . . . » Independent

 »Deftly weaves themes of forgiveness, belief and spiritual regeneration » The Times
The Discworld novels can be read in any order but Small Gods is a standalone.