This is a long-running series and it varies in tone as author Matt Wagner ages, It starts as a supernaturally-tinged crime/supervillain series and we often come back to this era. Future incarnations of the character add science fiction and post-apocalyptic elements. Epic, pulpy, sometimes uneven, and often a showcase for some surprising experiments in comics layout and pacing.
From Wikipedia: "Grendel is a long-running series of comic books originally created by American author Matt Wagner. Originally a noir comic in the style of European titles such as Diabolik, it has evolved into, in Wagner's words, a study of the nature of aggression. In 2009, Hunter Rose, the first Grendel, was ranked as IGN's 88th Greatest Villain of All Time."