I'd say it was unique, but Friday the 13th had an equally good series like this based around an antique shop. And, of course, it is like the X-Files and Warehouse 13 and Mellinum...but there are reasons that shows like this are made and develop a cult following. They are almost always really good.
I think the draw back to the show is that it has the title "Poltergeist" and like "Friday the 13th" that kind of set people up for a let down when they realized that it had little to do with the movie franchise.
But, if you accept that it's not based around the film franchise, you can sit down and experience a very entertaining horror show that should have been far more popular.
