Whoa boy, where do I begin with this one...?
The story is very compelling and you're going to get integrated into it. Due to the choices you make effect the outcome of the story, you may be thinking you want to see one certain ending and try to head for it. But then you're going to find yourself answering honestly. The thing this game does perfectly is pulling it's players into the story. You become Vincent as he struggles to stay alive in his dreams and choose what you think is best. Also as you play through it, you meet people at the bar and, well 'sheep' in the nightmare stages throughout your play. Now this game does one things very few games can do, and that's making you feel for a lot of the characters. You're going to feel at least one emotion for characters as you learn about their lives and struggles, and that's very rare for a game to flesh almost each and every character you can talk to.
Gameplay wise for the nightmare levels, if you're a casual gamer who isn't used to challenges... Be warned when getting this game. Catherine will push you to the limit where you're probably going to be screaming at the tv and throwing your remote down in frustration. This game is not to be taken lightly of at all. First off, puzzles can be quite challenging at times. There are many different blocks that appear as you continue to climb your way up to freedom, and you're going to gave to find how to use them correctly, or end up dead. Also you WILL get a sense of panic and urgency because you can not waste time in this game.
The reason for this is either a freakish monster is chasing after you, or the blocks below your feet are falling down as a consistent pace that you cannot waste time. You will learn over time how to build your stairs to the exit though. And when you finally reach that exit point, you're going to feel a sense of relief and accomplishment that is magnified compared to most other games.
Catherine has 8 possible ending so it has a lot of replay value as well. You're going to find yourself wanting to see all the endings for this game.
All in all, if you are a hardcore or story-driven gamer, then this is one game you cannot pass up. Catherine is going to leave you on the edge of your seat while the story plays and while you're climbing up the block puzzles. It's a very unique game that's going to draw you in, keep you there, and leave you wanting to go back for more.