A tense, fascinating adventure
I have long been a fan of visual novel-style adventure games for the DS and 9 Hours, 9 Persons, 9 Doors (999 for short) definitely stands up well among its genre-mates. 999 is about a group of 9 strangers who have been abducted and taken to a ship where they must complete a life-or-death puzzle game within 9 hours in order to escape.
The puzzles in 999 all involve escaping rooms. You will enter a room with a number of companions and together you will need to figure out how to unlock the exit door. In every puzzle, all of the materials that you will require to solve it are in the room with you. There's no need to worry about retaining items left over from previous puzzles or realizing that you need to backtrack because you missed picking something up. If you can find a way to unlock the exit, you're good to go and you haven't missed anything (though sometimes you will be kept behind by one of the other characters to discuss something). All in all the the puzzles are challenging and logical in a way that I found to be far more approachable than the obtuse, video game logic found in a lot of other adventure games.
At times, navigating your way through the puzzle rooms to find clues can be a little frustrating. You are provided with a map of the room you're exploring, but you can not look at it and navigate at the same time. In order to look at the room map, you must stop, open the map command to figure out where you are, and as soon as you start to move again, the map is gone in favour of a first-person view of the room. This can make navigating your way around several rooms that all look the same (this happens more often than I'd like) a little frustrating -- especially if you do like I did and stop using the map entirely.
The story, which is really the most important aspect of any adventure game, is phenomenal. It keeps you guessing right until the end and while the twists are always surprising, they don't feel at all ridiculous because really, they've given you the information you need to figure a lot of it out already, you just need to put it together the right way. The characters were all nicely developed and the dynamics between all of the characters in this messed up situation were always interesting to watch. I would say more about it, but there's no way I'd ever want to spoil it for anyone -- it's so good that I really just need to tell you go to play the game.
It is worth noting that 999 requires a minimum of 3 playthroughs in order to discover the game's "true" ending. Each time you discover an ending, you will be able to start the game again with memories of earlier playthroughs, thus allowing you to fast forward through story and dialog that you've already seen. Some critics have cited the fact that you cannot fast forward through puzzles on subsequent playthroughs to be a major downside to the game. While it can be a bit frustrating at times, you will find that the dialog changes significantly depending on which ending you're on track for. For example, a scene between the progagonist and player-character Junpei and another character in a single puzzle room can be completely different if you're on the "true" ending route than for other endings. The fact that at key moments there will be new dialogue allowing the player to see how the choices available to them can change the outcome of the story, in my opinion, far outweighs the annoyance of having to do some puzzles multiple times. Nothing a few pages of notes won't take care of.
I wholeheartedly recommend 999 to anyone who likes adventure games, especially visual novel-style adventure games. This game would totally have been in my top 10 if I'd played it in 2010 (and likely pretty high up on the list). It didn't ship a lot of copies in North America, so it may be a little difficult to find, but tracking it down is well worth it.