Good coop games on Steam Sale to play with the gf?

You know, I've been watching a playthrough of it and it made me think about it.

The Return of the Obra Dinn isn't really a co-op game, but I've also seen two other playthroughs where two people worked together on it. The premise is that you're an insurance inspector assigned to figure out what happened to the crew of the Obra Dinn, a ship that disappeared a few years ago and just drifted back to port. Your job is to figure out the fates of all sixty people that were on board including their names, how they died, who (if anyone) killed them, and the location of anyone who's still alive. To help you in this, you have a magic pocketwatch that lets you see the exact moment of death for any corpse you find.

It's basically a giant logic puzzle. You look for clues in the snapshots of death that help you match each person with their fate. Using a crew manifest and an illustration of the entire crew, you match the faces to the names and fates and along the way, you learn the story of what happened to the ship.