Apocalypse The Risen is a great product. It is unique among 3rd party products in that it is completely independent from all of the feats, races, classes, and everything else from official and 3rd party sources. This radical design means that Apocalypse The Risen is probably not for every table. While you probably could drop in features from other sources, the authors' recommendation to only use AtR and limited core material allowed them to take a very different direction than you usually see. It is defined as much by the races and classes it includes as it is by the lack of high-fantasy trappings.
I'd say the mechanical theme running throughout the book is "almost familiar." You can look at something and say "that's almost a tiefling" or "that's almost a paladin," but everything is built from the ground up specifically for a post-apocalyptic setting in which angels have fallen, demons risen, and the very depths of Purgatory shaken to their core. In lieu of a traditional fantasy setting, this game unequivocally takes place on Earth, in some hybrid lovechild of Constantine and The Walking Dead.
Apocalypse the Risen is built for people who want a break from the usual. Buy it if you want a gritty, survivalist game with low magic that's incredibly well-written. You won't find anything else like it.