Chess variants seem to come in two main flavors. In the first, new pieces, rules or squares are added to create a chess-like game that expands the decision-making tree. I haven't done a survey, but this seems to be the most common kind of variant.
The second type of variant takes the familiar pieces of chess and places them in some new environment. This usually creates a game that isn't very chess-like at all, although it can fool you at first. I think the game effect is to create a feeling of delight as you get to see something familiar in a different light. Bosworth (reviewed earlier) is that sort of a game, and so is Tile Chess.
Tile chess appears to dispense with the game board, as players lay down tiles bearing the image of the standard chess pieces and then, once all have been placed, move them in accordance with the standard rules of chess, with once exception. Pawns in Tile Chess can move one space orthogonally in all four directions and capture diagonally in all four directions, instead of just "forward" as in standard chess.
I say "appears" to dispense with the board, because it's really still there, just "virtual." Tile Chess can be played with no changes on a visible grid, and the designer even suggests people do so if it helps them visualize things. Indeed, this might be a use for those unwanted copies of Warmaster Chess 2000!
The actual fundamental rule of Tile Chess is the Unity Rule, which requires that every piece must end its move adjacent to some other piece orthogonally or diagonally and no piece can move in such a way as to break the chain of pieces of stranding a piece. Most of the rest of the rules in the game deal with the implications and complications of this rule.
What you end up with is a game that resembles a knife fight between opponents tied at the wrist. Unlike standard chess, which unfolds with a development phase and involves maneuvering for advantage over the course of several turns while building combinations of supporting pieces, Tile Chess is a bloody close-quarters brawl. Players start fully intertwined and pieces will fly off the playing surface at a rapid clip. The game can be played with up to six players, which will make chess-style long-range planning nearly impossible.
The rules include a few variants for set-up and play, including rules for combining Tile Chess with Knightmare Chess for those who need their chaos squared.
Tile Chess is a wild game. It's really too chaotic to develop much in the way of game theory, particularly in multi-player versions, but it's a fun filler. Games will tend to end quickly and decisively because a player who captures an enemy king can add the surviving pieces from that army to his own, meaning that it's possible to swiftly acquire a dominating board position with a well-timed capture.
About the only caveat I have about the game is that purchasers may find the components a little on the cheap side for the price. All the game is comprised of is a four-page rule book and 96 rather thin tiles with chess icons contained in a thin box. While the $9.995 price isn't steep, it still seems that the components don't justify the price tag. I would have preferred more substantial, euro-style tiles that could stand up to repeated playings.