Black Book is a dark RPG adventure game set in a world inspired by Northern Slavic mythology. Players control Vasilisa, a young sorceress who seeks to uncover the secrets of the titular Black Book. The game blends card-based combat with adventure elements, tasking players with solving riddles, completing side-quests, and confronting mythological creatures.

Gameplay centers on Vasilisa's quest to break the seals of the Black Book, utilizing a collection of spell cards and skills acquired throughout her journey. Players can send demons to perform tasks, but must manage them to avoid negative consequences. An in-game encyclopedia details the folklore and mythological creatures encountered, drawing on expert anthropological research.