Before buying the game, it is important to read this page, it explains a bit what awaits the player in this episode :
http://www.penumbrarequiem.com/site/
Quote:Penumbra: Requiem is to be considered an epilogue to Penumbra: Black Plague and not as a new episode in the Penumbra series. The main goal with Penumbra: Requiem has been to focus more on the physics puzzles and to see how far the current game engine could be pushed. This has made Requiem into a game that focuses more on gameplay and puzzles than the previous Penumbra instalments and a game that is more experimental in nature.
Although having a strong emphasis on puzzles the game still features a dense atmosphere, a trade mark of the Penumbra series. In Penumbra: Overture the goal was to induce strong fears from isolation, in Black Plague a main theme was paranoia and in Requiem you'll find a nightmarish and feverish atmosphere.
Penumbra: Requiem is an attempt to deliver a fresh and rewarding experience and not just some rehash of previous material.