What is Knightmare Chess exactly? It's chess with cards, strange and vicious cards which let bishops swap places with rooks, let pieces move through each other, let pawns move like kings in checkers. The first time you play it, it seems like an attempt to turn chess on its head, throw strategy out the window and have fun with chess pieces. As you get to know the game, it combines the complex boardplay of chess with the art of deck design associated with collectible card games like "Magic The Gathering (TM)".
Knightmare Chess was first released in 1996 by Steve Jackson Games, the makers of GURPS (the Generic Universal Roleplaying System), Illuminanti and a number of other cool games. The game is a close relative (some have called it a rip-off) of a game called "Tempete sur l'Echequier", released in France by game designers Pierre Clequin and Bruno Faidutti. (To be perfectly fair, SJ Games credits Clequin and Faidutti in the game material and on their site.) Near as I can tell, SJ Games has turned the cartoonish art on Tempete into lush, dark, foreboding cards, radically expanded the set of available cards and clarified some rules. (For more on Tempete, check out this site The net result is an extremely well-balanced and challenging board game. With a second set of cards released in 1998, the game has gotten yet more complex, and, IMHO, more interesting.
I've found Knightmare Chess to be a great game both for chess players and non-players. A good deck is capable of destroying any advantage a good chess player would normally have, which makes KC a terrific equalizer for chess players of differing abilities. Unsurprisingly, most chess "purists" tend to hate the game. (The author of the "chess variants" homepage rips the game for artwork which he finds overly disturbing. I suspect he doesn't like it because it forces you to throw most chess strategy out the window.) Playing regular games with friends, I'm beginning to suspect there's at least as much strategy in KC as in chess, though it's a radically different form of strategy.
Knightmare Chess is, theoretically, a collectible card game. That is to say, you can buy multiple packs of Knightmare Chess cards and craft decks using multiple instances of cards. I've never seen folks play the game this way since every pack of KC and KC2 cards contain the same cards, eliminating some of the element of surprise! Furthermore, the cards are quite expensive, preventing most people from buying more than one set at a time.
I'm not sure why Knightmare Chess hasn't enjoyed the widespread success of a game like MagicTG. I suspect it's got at least two factors going against it. One, since it's chess-based, folks who don't enjoy chess (or are scared of it) are less inclined to take the game on. I think that's a shame - the game favors folks who know chess a little, but aren't masters, and gives a novice with a good sense for card games the chance to satisfyingly trounce an overconfident grandmaster-wannabe. Look at most collectible card games and tell me they're not hard to learn! Knightmare Chess may have a slightly less steep learning curve than some of the other popular games on the market today. Second, since Knightmare Chess hasn't developed as a collectible card game, it's needed to get converts on its own merits, not through the "trading card" market MagicTG has exploited so well. I suspect that if KC "starter decks" cost $5, with expansions available for under $3, this game would have an extensive trading card market and a tournament circuit. C'est la vie. At least I've found a group of people to play it with...