I only played the demo, which for me lasted 57 minutes. As it ends at a particular point in the game, how fast you are able to play it will determine how long the demo is for you.
I thought the story was pretty lame up to the end of the demo, which ended on a mild cliff hanger, but it might get better. I had quite a bit of trouble with two of the HOGs due to small, dark objects. The puzzles were nothing new, but there was an even balance of puzzles and HOGs. .
A very sudden ending and the repetitive music were annoying, but not critical.
I subtracted a star for the very frequent need to use the hint button in HOS due to very small or dark objects, as well as object names that needed translation to English, and/or objects that looked like something other than what they were supposed to be.
I subtracted another star for the lack of hints outside of the HOS which made it necessary to exit the game repeatedly in order to look at the walkthrough. It also would have been helpful to have a map.
I would have liked to subtract half a star for the annoyance factor of too many HOS (I can't believe I'm saying that). The only way I can describe it is, it made the game sort of hobble along with too many unnecessary interruptions.