This tutorial instructs on finding the Artbook and Soundtrack for Punch Club Game:
If you're an owner of the Deluxe edition of Punch Club, you can find the folder with Artbook and Soundtrack the following way:
1. Select "Punch Club" in your library, right click it and select "Properties".
2. Proceed to tab "Local files" and select "Browse files"
3. You should have a folder with Artbook and DLC opened