Yeah, the game pretty much stays the same until the end(box puzzles and such) and I know what you are talking about when you say you play a little then just stop(took me a couple months to play through the whole thing because I got bored)but near the end the story line kind of picked up and I couldn't stop playing for a while.
I don't know if you've seen the ending so I won't spoil it but it actually sets up a sequel at the end, why they haven't worked on it is beyond me. If they got rid of the annoying box puzzles it would probably be one of my favorite games