Abalone's one of the better modern abstracts. The rules are straightforward, it introduces a new conflict-resolution technique (pushing) and it looks real nice. I just can't figure out why it's named after a fish!
The basic game is two-player and while I haven't exhausted all the potential of the standard set-up I see from its Web site that there are dozens of variant set ups, which is another attributes setting it apart from most abstracts.
There are also rules for multi-player versions. although both the even-number versions (4- or 6-player) are team games. The 5-player version puts the fifth player in the middle of the board, handing him/her the key location in the game, although at a cost of one marble. I haven't played that one, so I'm not sure how that will work.
I have played the 3-player version a little bit, though. It's the most like the 2-player game in that it's every man for himself and all players start even in material and position.
Unlike the 2-player version of the game, with three players it's harder to put together a strategy. One has to play more opportunistically because the board changes configuration twice in-between your moves. Not only that, but it's harder to anticipate those changes because you can't be sure how the other players will interpret the board situation. In the 2-player game you're each working directly against one opponent, but in the 3-player situation there's additional dynamics at work. Each of your opponents has to choose each turn who he will concentrate on. it's very rare that there's a single move available that hurts each opponent equally.
On top of that, there's the problem of massing enough force to execute an offensive. The defense is the stronger form of warfare in Abalone anyway and in the 2-player game it can take a few turns of maneuver to set up a good attack. But in the 3-player game each player only represents one-third of the potential offensive power, instead of half. Or another way of looking at it is that a player in the 2-way game is attacking at 1-1 odds while in the 3-way game you're fighting at 1-2 odds.
The three-way dynamic helps keep the game from bogging down in a stalemate. The situation is inherently less stable than the 2-sided game. If one player is weaker than the other two the game can devolve into a race to see who can beat up the weakest one fastest and get to six marbles. If one player gets picked on and loses 3 or 4 marbles they can lose almost all offensive ability.
The game still works as a three-player game, although I think it's more chaotic than the 2-player game.