I bought it a few months ago and it's worth $10 used. I guess I'd call it an adventure game, but the controls/gameplay are secondary (by a long shot) to puzzle solving. I haven't finished it yet, but plan to soon. It plays like a classic PC game, expect to have a lot of patience if you play it. A lot of characters talking, very little action.
nice simple interface. it goes pretty much like this.
1. view image 2. click on something 3. figure out the puzzle
visually, the imagery is stunning. lots of nice atmospheric type of stuff.
the puzzles aren't too difficult. i think i did have to use a faq for a couple of puzzles, but not many.
the story is probably one of the best things. very tight, interesting plot.
one thing i really liked about it (which a lot of people hated) is the static nature of the puzzles. no looking up, down, left, right, etc. everything you need to see is right there.
the interface is decent...but be prepared to do a lot of walking.