Small Gods (Discworld book 13), Terry Pratchett

ou 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 . .

. The Discworld novels can be read in any order, but Small Gods is a standalone.