One of the most underrated in my whole collection. I blame the horrendous box art for the poor sales; the game itself is just excellent.

I have to agree - I found this in a bargain bin, didn't expect much from it, and it totally took me by surprise.
It's sort of like a squad-based tactical combat game, only with less combat and more 'The Sims'. There's a wide range of ghosts/spirits/elementals/gremlins/etc. to choose from when assembling your squad, an interesting variety of non-linear objectives in each mission, great gameplay and puzzles, fantastic music and level design..it's definitely worth checking out.

I liked this game too; played through it three times. I even bought the Steam version just so I could play the bonus level from the UK edition.

The poor sales in the US were probably due more to a lack of advertising than anything. I followed GM's development and bought it at release, but the official forum's (low) population was always overwhelmingly British.
I agree that it's a great game, although it tends too much to the puzzle side of things for my tastes. I'd rather have a bit more freedom in how I approach each problem. In fact, a sandbox option would have been great, where I could just run around scaring people in any way I like, just for the hell of it.

Advertising was definitely the problem in the United States. I first found this in a bargain bin many years ago. Initially, I didn't think much of it since I had not heard of it and the box art is reminiscent of low-budget software designed for young children. However, I was browsing for something new to play, and the description and screenshots on the back of the box piqued my interest. So, I ended up buying it - just to try it.
I'm glad I did.
While the game's engine borrows heavily from the Sims, it has so much atmosphere and creativity that I was floored. It was clear that the developers worked hard to make this game interesting, and the sights and sounds you get when you start whipping up a location into a frenzy...I just love it.
This is one of my favorite PC games ever made, and I'm sad that a sequel will almost definitely not happen. While I still have my CD copy, I bought this on GOG just to be certain I will have this game for years to come.

I really loved "Ghost Master". I loved the premise, and the characters you get to use are pretty awesome and memorable.