A fun puzzle game, but not much of a finish for the series.
Your'e faced with a series of puzzles and hardly any story. The cryptic dialogue from a couple disembodied voices is the only thing that ties this game to the Penumbra series until the very end when it comes full circle.
I get what it was trying to do, but I feel like it could have played up the idea so much more. It was rather anti-climactic, but luckily it tied the end up satisfactorily, at least for your character.
If you've played the first two, you would probably like this okay. It's fun and had a couple spooky moments, just don't expect much more than a moderate-difficulty puzzle experience with a spooky theme.