The core mechanics are heavily based on Into the Odd if you're familiar with that, but the major innovation is the Karma system.
It's very rules-light and fast-paced. The Karma system incentivizes engaging with the NPCs and interacting with the world in Buddhist-inspired and non-violent ways, and psychological exploration, but it doesn't shoehorn you into a particular style of play and if you want to get into scifi/fantasy fights you can do that too.
The module in the book gives a sets up a Poltergeist Investigation, an adventure in one of the Numberless Courts of Hell, and it demonstrates how to think of Karmic Attachments and how to set up those situations.