In 1995 the Cthulhu RPG had no home in Germany. A new company called "Ars Ludi", in cooperation with Queen Games, started to produce scenario book, mostly reprints of older Laurin publications. Ars Ludi didn't have a license though, so Chaosium forbid them to sell the already produced supplements. That was the end of this project, but it was many years later that the already produced books somehow started to appear on the market and got sold normally and unoffended by Chaosium in german RPG shops.
This is the core rulebook based on the 4th edition by Chaosium (actually a reprint of older Laurin issues) but also contains an original new german scenario called "Nördliche Breite" ("Northern Latitude").
Though it contains the core rules, the mythos background is described in a separate book.