North Against South on the Gettysburg 50-Yard Line : LET THE BAND PLAY DIXIE<i> by Lawrence Wells (Doubleday: $17.95; 391 pp.) </i>

Let me enthuse: Lawrence Wells has become a master of the “What If?” novel; what’s more, he tells a tale that’s funny, touching, pertinent and relentlessly rich with wacko, wild, weird and fundamentally decent characters.

The imaginary premise of Wells’ first book, “Rommel and the Rebel,” was that Nazi general, Erwin Rommel, came to America in the 1930s to study the military tactics of a Confederate general, Nathan Bedford Forest, which he later utilized in North Africa and which, because of sleuthing by a young U.S. Army officer, were eventually turned against him.

In this, his second novel, Wells expands on the device wonderfully. It is 1896, and a New York gambling magnate has decided to stage a North-South all-star football game in order to gain respectability in the stodgy Victorian society of Philadelphia. Coaches selected are the giants of the day: John Heisman (of Heisman Trophy fame) and Glen (Pop) Warner for the South; Amos Alonzo Stagg and Phil King for the North.

The gambling king, a faro-playing Irishman named Richard Canfield, who once bet a man $50,000 on how long it would take a raindrop to run down the window of a train, has decreed that the match will be free from betting and corruption. He has enlisted the Philadelphia Athletic Club to sponsor the game, with proceeds ostensibly going to charity. Moreover, the honorary chairmen of the squads are: for the South, former Confederate general, James Longstreet, Lee’s second in command at Gettysburg, and his opposite number, retired Union Army general, Daniel Sickles--neither of whom know the first thing about this new game of football.

Enter now a cast of some very funny characters: an assistant coach, history instructor and Civil War nut from the University of the South (Sewanee), Cornelius Humboldt, who has been placed in charge of recruiting several players; Chase Riddle, one of his recruits, a stellar quarterback at several colleges until he flunked or was thrown out and who is now assistant pastor of a fundamentalist church in Kentucky; I. Lopez, a 40-year-old Hispanic drunkard, gambler and con man who euchred his way onto the team, and Kate Kuykendall, old-maid mistress of the Post Oak Normal School and her team of black players, presumably invited along as porters.

Also fielded for the South are some of the great college names of the day: “Blondy” Glenn of Auburn, “Cow” Nally of Georgia and others. Opposing them are the finest Northern players of that era: W. W. Heffelfinger of Yale; Edgar Allan Poe (nephew of the poet) of Princeton, and so on.

In addition, an aging former Confederate soldier and professional gambler, Hudson Stroud, who is also grandfather of Chase Riddle, the South’s quarterback, decides to come along after he learns that the North’s quarterback is none other than the grandson of his old military and poker-game nemesis, Ernie Libowitz of Michigan. Thirty years before, Libowitz had captured Stroud’s sword during a battle in which Stroud lost a leg, and he intends to win it back from Libowitz in a poker game.

As it turns out, the blacks from the normal school prove far better football players than the all-stars from the South’s colleges and wind up starting the game. This causes a near riot in Philadelphia, which is spurred on by activist W. E. B. Du Bois. The Southern team is put up in a house of prostitution, and at the urging of Du Bois and several others with wildly conflicting interests, the first player’s strike is instigated. Meantime, a poker game of monumental proportions is in progress involving Stroud, Libowitz, Longstreet, Canfield, the faro king, and just about every other card sharp and riverboat gambler of the period.

As a subplot, Wells calls on his extensive knowledge of the Civil War to set up a number of touching scenes in which old Longstreet, who was blamed by many for Lee’s defeat at Gettysburg, and Sickles, who was credited with the victory, rehash that fateful battle. Meantime, Longstreet has become interested in the game of football and finds it just another form of war. He decides to read coach Stagg’s classic treatise on the game. Stagg, who sees war as just another form of football, avails himself of Longstreet’s book on Gettysburg; each, thereby, hoping to outfox the other by understanding his theory of tactics.

Because of continued rioting in the Philadelphia streets over the contest--which by this time has attracted national attention--it is decided to move the game to Gettysburg itself, and the two old generals are assigned to go there and lay out the field of play. What then follows is a football game on a par with that in the movie “MASH.”

Once Wells sets up his story, there’s just no stopping it. And it’s not only his intricate detailing of football, gambling, the Civil War or turn-of-the-century Philadelphia that makes this novel work, it is his clear perception of truths of character and the rare ability to make us smile knowingly and even laugh out loud.