If your goal is to learn or replicate the art style (characterized by heavy blacks and high contrast), visual guides are available: One Source Lighting (OSL) Tutorials : Specific video guides like Craftworld Studio's Tutorial
If official retailers are out of stock, collectors often turn to secondary markets: darkest dungeon art book pdf
While there is no "free" official PDF version of the Darkest Dungeon Art Book If your goal is to learn or replicate
Spans over 200 pages in some expanded editions, detailing character designs, creature ideas, and thematic mood boards. Artistic Influence and Style detailing character designs