Games like Somnolence
Games like Somnolence include ROUTINE, SOMA, Mouthwashing, KARMA: The Dark World, and SIGNALIS. We matched them by the tags players give Somnolence on Steam (Atmospheric, Psychological Horror, Surreal, Sci-fi, and Adventure): closest matches first, and among equally close ones the better-known games.

ROUTINE
Shared: Psychological Horror · Atmospheric · Sci-fi

SOMA
Shared: Psychological Horror · Atmospheric · Sci-fi

Mouthwashing
Shared: Psychological Horror · Atmospheric · Surreal

KARMA: The Dark World
Shared: Psychological Horror · Atmospheric · Sci-fi

SIGNALIS
Shared: Psychological Horror · Atmospheric · Sci-fi

Outlast
Shared: Atmospheric · Psychological Horror · First-Person

The Beginner's Guide
Shared: Atmospheric · Surreal · Adventure

The Talos Principle
Shared: Atmospheric · Sci-fi · Philosophical

MiSide
Shared: Psychological Horror · Atmospheric · First-Person

Iron Lung
Shared: Atmospheric · Psychological Horror · Adventure

POOLS
Shared: Psychological Horror · Atmospheric · Surreal

Fears to Fathom - Ironbark Lookout
Shared: Psychological Horror · Atmospheric · Adventure

[Chillas Art] The Convenience Store
Shared: Psychological Horror · Atmospheric · Adventure

Summer of '58
Shared: Atmospheric · Psychological Horror · Thriller

Superliminal
Shared: Surreal · Psychological Horror · First-Person

Visage
Shared: Psychological Horror · Atmospheric · Adventure

Subliminal
Shared: Psychological Horror · Atmospheric · Thriller

No, I'm not a Human
Shared: Psychological Horror · Atmospheric · Indie

Still Wakes the Deep
Shared: Psychological Horror · Atmospheric · Adventure

MOLE
Shared: Psychological Horror · Simulation · Adventure

Half-Life 2
Shared: Sci-fi · Atmospheric · Adventure

>observer_
Shared: Psychological Horror · Atmospheric · Sci-fi

Layers of Fear (2016)
Shared: Psychological Horror · Atmospheric · Adventure

Fran Bow
Shared: Psychological Horror · Adventure · Atmospheric