Now it's clear that the book seriously strawmanned Christianity: in our world, the argument is whether God exists, but in the book He definitely does so it should be a deeper, more interesting question - if you know for a fact there is a God, should you follow Him?

But it ducks that at every turn. "We should follow Him to get to Heaven" becomes "Nah, that's a lie"; "But He created us!" is "Nope: that guys been deposed". The story pushes the side of Azrael by making religion a lie even though God exists, which isn't playing fair.