Simon Spurrier 
Six-Gun Gorilla #1 [EPUB ebook] 

Welcome to "the Blister" — a bizarre other-world colonized by humans sometime in the 22nd century, which quickly became a hotly-contested source of fertile land and natural resources long ago exhausted on Earth. In this new frontier, a rogue gunslinger and his companion wander across a wilderness in the grips of a civil war, encountering lawlessness, natives, and perversions of civilization in a world at the crossroads between the past and the future. The fact that said gunslinger is a bio-surgically modified silverback gorilla toting a pair of enormous revolvers is neither here nor there.