The 1st edition of Warhammer Fantasy Role Play is one of those systems that oozes with a dark and hopeless atmosphere. The characters are usually very ordinary people, sometimes powerful, but always fighting a war against Chaos that seemingly cannot be truly won.
The setting is an alternate, fantasy medieval Europe, like many D&D setting, but it is very different in tone. Humans, Elves and Dwarves do exist in Warhammer, as do Orcs and Goblins, but their roles are all diminished in comparison to the power of the horrific creatures of Chaos. The Middenheim : City of Chaos supplement is an example of just how deeply Chaos can warp a once lawful and pious society. It was originally entitled "Warhammer City", but it was revised to include more info and to fit in better for play with the last part trilogy of adventure modules, but it can be used as a stand alone item. Like any WFRP 1st edition items, it is a bit harder to track down, but not impossible.
Set near a woods infested with Beastmen and south of spawning grounds of mutated Chaos creatures, the city of Middenheim has held the line against the twisted forces Chaos, but now it has become slowly corrupted from within. The first section of the book, Power Behind the Throne details the convoluted conspiracy and infiltration of minions of Chaos inside the city Middenheim.
Middenheim is in some ways like a Warhammer version of the City State of the Invincible Overlord. Many organizations, shops, notable persons, places of interest, etc. are detailed in the gazetteer, which is most of the book. It does this similar to the CSIO by district. Puns are found throughout the book in name places and descriptions and such, which can be something a GM likes or dislikes, depending upon the flavor of their game - these can be easily changed if need be. The undercity is the most infested area of Middenheim and adventurers that journey down into it may never come back alive... or untainted.
The supplement comes with maps and the strange illustrations that all WFRP books have and encounter ideas an plenty of any other goodies to keep a Warhammer lover drooling like a Chaos mutant. If you ever find a copy, it is worth grabbing.