Plenty of useful reviews already, so I'll keep this short: Based on the description, I was prepared for some fun weird-western pulp. But I was surprised to find a lot of substance in the dark-fantasy-horror vein. Plenty of unique and fleshed out characters. And a surprising side-story on the dawn of creation, the fall of angels, and other myths and theologies given nods. It felt like if Stephen King and Neil Gaiman made a dedicated western. 
 Really enjoyed it, 4.5 stars, and will be looking forward to picking up the sequel soon!