I thought it was very interesting, and also a great game for the girls (no fanservice and cute guys, lol).
It's quite short and not that challenging but very entertaining.

Here's the opening movie for you: http://www.youtube.com/watch?v=sACLmz5j3BQ
And here's the synopsys as well:
Time Hollow follows the story of Ethan Kairos, whose parents, Timothy and Pamela Kairos, mysteriously disappear on his 17th birthday. Ethan realizes that the entire world has changed as if his parents had disappeared 12 years ago. Ethan then finds a note tied to his cats collar telling him to look in a dumpster behind his school and he finds a Hollow Pen, an uncanny object with the unique power to open portals to the past, as well as a note from his parents. Ethan uses the pen to solve problems that suddenly and mysteriously occur, thus changing the present, though he himself is able to remember these past parallel universes.