Darkest Dungeon is now officially available on Steam for Windows, OS X, and Linux, following a successful run on early access. This lengthy post outlines the history of this project and the many changes present in the release version, and here's the official description of the game:

Darkest Dungeon is a challenging gothic roguelike turn-based RPG about the psychological stresses of adventuring. Recruit, train, and lead a team of flawed heroes against unimaginable horrors, stress, famine, disease, and the ever-encroaching dark. Can you keep your heroes together when all hope is lost?