I love Good Omens too, for those very reasons. :D (Well, and that I adore the writing of both co-authors.) I'm an atheist-leaning agnostic, so as you can imagine I'm pretty allergic to being preached to.

I, Lucifer is heavier on the theology and rather less flippant, but it's firmly on the side of humanity, and the themes are very much about humans and what we do to one another.