This is a decent (and only decent) adventure game by Microïds, the people behind the masterpiece "Syberia"
Save for the nicely done cut-scenes, the game is a very simple dvd-player style adventure (the kind where you "jump" around, from location to location, rather than pointing and clicking over 2D backgrounds to move true 3D characters, like Syberia, for example, and it's light-years away from modern 3D adventures like Dreamfall). Its puzzles are slightly easier than average.
The characters and things you can interact with are 3D, though, and while most of the time the game looks fine enough, there are some situations where the mix between 2D backgrounds (in some locations they are simple flat images, and at some point you just have to think that the developers were far too lazy to improve them a bit) and 3D objects or characters is horrendous. Despite that, the game plays fine, it's not overly complicated (but still challenging enough), and it's got some interesting music (although after a while it does become repetitive sometimes and a bit annoying - specially when you are stuck on a puzzle while listening to the same background sound loop again and again...) The game has some nice scary moments, sometimes truly hair-raising. It's more of a psychological type of terror, you get scared of the flashbacks and visions that you see on the screen sometimes, the scenes of the murder (from the beginning) are truly disturbing, so careful with who plays this game - it's not for kids!! I jumped on my chair several times while playing - but, to be honest, i easily jump on my chair even with mildly scary games.
All in all, it's a decent adventure game, not specially nice or horrendously bad, it's just got nothing to do with Syberia (a shame, because we all love Syberia, don't we?) and it shows its age. While it can still be played fairly well, when you realize the limitations of its graphics engine it kind of leaves you half-satisfied. I seriously was expecting something more.
But Post Mortem is neither bad, nor brilliant. The best thing is that it doesn't require a powerful machine to run it, some cinematic scenes look nice, it's a by-the-book 100% traditional point & click adventure, the interface is extremely easy to use and the story is, well... yet another take at Broken Sword (mysticism, murders, Paris, detectives...) so it is likely to appeal to adventure fans - if they are not bored of going through the same stories again and again.
I got slightly disappointed when i bought this game (good thing it's now for next-to-nothing on budget editions) because it advertises itself with "made by the authors of Syberia" - and indeed it doesn't have anything to do with Syberia. I was expecting the same kind of engine and interface, and it's a much older-looking adventure game.
Still Life is a much better game, with a similar story, and it's done better. There are plenty of similarities between Still Life and this game, only that Still Life has proper 3D models and a much less outdated technology.
Anyway, if you REALLY like adventure games about murders, strange mystical forces and private detectives, then get this game as it's really cheap now and you'll possibly enjoy it, providing that you don't have any other new games to play. If I was to choose, I'd rather get Still Life, but if you have finished that and are desperate to play something similar - if older - then Post Mortem can be a nice&cheap option.