The game is a solid and enjoyable 2000's FPS but very obscure and hugely overlooked because:
1. The KISS branding immediately turned off a number of potential players.
2. KISS fans who did buy were angry that you didn't play as the band members of KISS, generating dis-proportionate negative feedback at the time.
3. Deus Ex released a month prior hugely overshadowing it's release.
Based on a short-lived run of comics between 1997 and 2000, the game borrows the characters from the comics to tell the story of an inter-dimensional evil that has corrupted the realms of Waters, Earth, Air and Fire. As such you play as the a group of humans chosen to awaken the avatars of each realm (the KISS stage personas), to do battle with the Nightmare child.
Now, i first played this game when it was a demo included on a PC Gamer magazine coverdisk, and immediately was gripped by it due to it's unique stylings. I played the demo (the water realm) through multiple times over the years before i finally managed to pick up a copy of the full game years later and i can safely say, it did not disappoint.
While there is not enough space here to extoll it's virtues in full, i will say that the unique amtmosphere, ambience and style set it apart from any other FPS, even today i don't think there is anything that matches it's particular design, from the very unique enemy designs like the Arachniclown, Unipsycho or the ever sinister chimes of the Organ Grinder, to the unique weapons such as the Scourge (Sniper Whip, also used for traversal), Galaxion (Black-hole) or Draco (a Shoulder Dragon that vomits lava).
The campaigns are also interesting and varied, riddled with lots of secrets to discover, each ending in a twisted Circus level, all accompanied by Will Loconto's ambient soundtrack which supplies ample cosmic dread.
KISS Psycho Circus - The Nightmare Child deserves a second chance on GOG, for others to discover and enjoy, though the KISS branding is likely to be a big obstacle.