It's rare that a RPG rulebook makes me laugh out loud, rarer still before the contents. But the "Note on Transatlantic Slang" managed it!
Stay Frosty's classes have been stripped out and replaced with the ranger - distinguished by traits and gear. Rangers are stronger than their SF equivalents but are up against the cursed hordes of the Doomed Dimensions. The sample adventure "The Flayed Domain" is a pointcrawl reminiscent of a Quake map.
This entire 80-page book is a love letter to the ilk of Doom, Quake, Hexen, and other 90s first-person shooter PC games. The art is visceral, the text has punch, and the PC life expectancy is limited at best.
If you want "Quake: the RPG" - get Slipgate Chokepoint.