Visual Novel + Room Escape + inventive story = instant classic
The first thing you have to know about 999: Nine Hours, Nine Persons, Nine Doors, is that this is not a game for the impatient. It's a visual novel, and if you want your plot, you will need to READ. A lot. The game deliberately takes a leisurely scroll through the text on your first playthrough so you don't button-mash your way through the dialogue. If you don't like reading, you will suffer a slow, slow death while waiting for your next set of puzzles. Your first taste of this occurs after you beat the initial puzzle; you are treated to roughly ten minutes' worth of reading before you choose your next puzzle.
Secondly, do note that there is no possible way of "beating" the game on your first playthrough, either, and the odds are against you managing to "beat" it the second time, too. Thankfully, all subsequent playthroughs from the second on allow you to fast-forward through text you've already read, though the dialogue is still unskippable. Again, this is a very deliberate choice. Any puzzles you've previously played can be played outside of the story mode, but you'll have to go through more plot (and potentially puzzles you've already solved) to reach new puzzles.
Speaking of playing new puzzles you've already solved, they do not randomize. Yet again, deliberate. In fact, instead of playing the game with a walkthrough, keep a pencil and paper handy for the different puzzles and story paths you take to get through the game. The game allows you to take shortcuts through puzzles if you already know the solutions; the very first one being a set of luggage combinations, and another one involving a shower tile. It's not cheating--in fact, I encourage it, and I believe the game does, too.
The puzzle segments themselves are also well-handled and widely varied. They touch on a variety of themes, from baccarat to naval navigation to the hexadecimal system, and combine that with your standard point-and-click adventuring. When you click a "live" hotspot, it is highlighted in its entirety so you know what other areas the game considers the same hotspot--a nice interface touch that keeps you from doing too much pixel-hunting.
Again, this is not a game for the impatient. You will spend a lot of time reading. You will spend a lot of time puzzling things out. This game is not Braid hard, but it takes time and patience to figure out how to "Seek a way out!" as the cutscenes command you to. Once you do, though, it is a very, very rewarding feeling, and the "You found it!" at the end of each puzzle sends shivers of anticipation down your spine, as you ready yourself for the next batch of plot.
You won't even have to wait to your next puzzle to get to the plot, though; most puzzles have brief intermissions in which you learn more about the back-stories of the people with whom you're trapped, whether it's the fanservice-tastic girl with a mean mouth, the mysterious man whose eyes remain firmly shut, your childhood-friend-love-interest, or the others. All the people who survive the game--and there are some who will not--are examined to varying levels of depth, whether they themselves are integral to the underlying plot or just show skills you'd never expect of them given their personality or appearance.
The art direction is extremely competent. The score--while not nearly as memorable as the score in the Ace Attorney games--sets the mood, and even the blips representing the dialogue of the characters as it scrolls across the screen (a different blip tone for each character!) contribute to the atmosphere. Adding onto this is the artwork, which more than adeptly conveys what you can interact with in the escape sequences and do a fine job of illustrating all but the goriest scenes (blood is shown, but the most graphic bits are only written) in the visual novel portions.
I am deliberately omitting a description and review of the plot for this game because, as was with Braid, it is best played with as little advance knowledge as possible. Not to mention, if you want that stuff, you can easily find it elsewhere on this site alone. The dialogue and narrative is more than competently translated and alternates between being downright hilarious (and intentionally!) and bone-chilling (again, when it needs to be). As for the plot, I will say it is engrossing and--when you get far enough, and you will know when you get to this point--mind-blowing. This is what makes it worthy of the praise it receives, and it is very much worthy of all that praise.
However, once you manage to finish the game and explore all the rooms and view the assorted endings, you won't find a need to play it over again for a while, much in the same way that finishing a book will let you leave it on the shelf for some time. Perfectly fine for a visual novel; unfortunately, due to the lack of randomization mentioned in the third paragraph (at least, where randomized elements are feasible), you won't be coming back to the game for the puzzles, unless you lose the piece of paper I suggested you use for writing down the solutions. The lack of replayability of the puzzles keeps this from being a straight-out five star game.
Do not mistake that missing half-star for a ding in an otherwise flawless car, however; while it is a 4.5-star game, it is a 5-star experience. 999 is more than worthy of your time. It manages to take the standard structure of the visual novel and fashion it into something that really could NOT be done in any other medium. If you're a bibliophile (or at least as long as you get some enjoyment out of reading), a ride from the beginning to end to end to end may take you the better part of two or three days, particularly if you uncover the bad endings first. Once you get to the "true" ending, and complete that last puzzle (of which I will say: puzzle-wise, it is a victory lap; story-wise, it is an appropriately awesome climax) and start reading the final scenes, the payoff is incredibly satisfying, and by the time you get to "THE END," you will be beyond satisfied.
