AMERICAN FALLS. By John Calvin Batchelor. Norton. 570 pp. $16.95. y Reid Beddow

IMAGINE A NEW KIND of Civil War novel. Imagine a long, ambitious, often comic historical novel every bit as good as Michael Shaara's The Killer Angels and Thomas Keneally's Confederates, but one in which the only battle is a minor skirmish whose telling consumes one page. That's right, a Civil War novel in which no heroes in butternut advance up Little Roundtop to assault heroes in blue while a band jingles "If You Want to Have a Good Time, Join the Cavalry."

Imagine, instead, a Civil War novel with characters who detest the seemingly unending slaughter and who will do anything, even betray their country, to stop the madness. Imagine other vengeful characters seized by terrible hatreds who can murder women and children; and imagine, also, amiable characters who aim to make a little money, or better yet, a lot of money, out of the killing. Imagine, too, a Civil War novel with believable black characters who are not cut- outs from Kyle Onstott's Mandingo.

Imagine, finally, an extremely well written work of fiction with pretensions to being an astonishingly detailed portrait of American society in 1864 and a philosophical treatise on the meaning of good and evil, original sin and man's fall -- if you will, American falls (the title again).

All this begins to describe John Calvin Batchelor's unusual, brilliant and compelling novel of the great rebellion, American Falls.

The title comes from the name of the American side of the Niagara cataracts, gorgeously flaunted on the dustjacket by George Catlin's 1827 painting, View of Both Falls From the U.S. Shore. Niagara is where the novel opens, as the train from Toronto enters the United States. Aboard are members of the Confederate Secret Service; it is 1864,he war is in its fourth year, Sherman has burned Atlanta, Lee is under siege at Petersburg and the desperate Confederacy clutches at straws. One straw is the disruption of the forthcoming presidential election, which pits a peace candidate, McClellan, against Lincoln; another straw is a plot to pass hundreds of thousands of tons of contraband cotton through the Union blockade, a transaction that will bring its vendors millions and the South food; yet another straw is vengeance pure and simple -- to carry the war into the North through acts of terrorism.

Clearly there is mischief afoot. A negotiated peace would perpetuate a divided nation. Who can oppose such infamy better than the fledgling United States Secret Service, led by that Napoleon of duplicity, Colonel Lafayette C. Baker? On the surface, then, American Falls is about the shadow war waged by spies, a subject full of tantalizing possibility with its Copperhead plots and daredevil agents. Batchelor leaves no antiquarian stone unturned to serve up his history in generous scoops:

"In 1864, no one, not Lincoln and his moderate and radical Republicans, nor McClellan and his so-called War and Peace Democrats, made a serious pretense that the issue of slavery could any longer justify the slaughter of the war, and any spokesman who maintained that the war must continue in order to free the slaves was likely to be stoned. The Election of 1864 was about peace . . . When? How? Who would bring it? And what would the peace look like?"

The lectures never obtrude. This is history as entertainment, and the facts for the most part are splendidly sugar- coated. Thus, the Republican boss of New York State: "No one in the nation was more dazzling or effective as king- maker than Thurlow Weed. It was said that he understood American politics, because he understood that, in a democracy, politics was the plain-dressed and plain-spoken pursuit of money."

The actual Secret Service duel between Johnny Reb and Billy Yank is personified by two strong, humane, thoroughly likable characters, whose adventures unfold in alternate chapters. One is John Oliphant, Philadelphia-born businessman and southern sympathizer married into an aristocratic Sea Island, South Carolina, family. (At times Batchelor hilariously parodies the languid plantation life; one half expects Scarlett and the Tarleton twins to turn up: "Cousin John, you are to go with me! We've already missed two suppers and two teas with them eye-popping at Chinaberry to fuss over you with their ways!").

The other main character is the luckless, though plucky, Captain Amaziah Butter, late of the 1st Maine Cavalry, now transferred to the federal Secret Service, "a horse soldier without a horse." He blunders deep into the Confederate plot, abetted by his black sidekick, the urbane Gouverneur Nevers, the touchingly pro-Union chief of detectives for Major General John A. Dix's Department of the East and a "monarch butterfly of a dandy."

Both Butter and Oliphant are sick of war and want peace; and there is another correspondence: both are adulterers. Their passions -- Oliphant's for his sister-in-law, and Butter's for a Washington widow -- are agreeably narrated and not thrown in for sexual relief. The two enemies, trapped in the "common wilderness" of war, struggle to understand each other, and never really do. Butter pursues Oliphant through a Confederate attempt to burn down New York City. He catches up with him at the novel's sensational, eye-popping climax in a howling blizzard under the cliffs and spray at Niagara Falls.

Batchelor, author of two previous novels, The Further Adventures of Halley's Comet and The Birth of the People's Republic of Antarctica, knows how to paint a scene. In American Falls there are several finely brushed interludes -- the gracious antebellum life on the Carolina barrier islands, the bustling commerce of the North (in the crowded bar of th Astor Hotel the war profiteers drink their whiskey and sing "We'll Hang Jeff Davis on a Sour Apple Tree!"), a contretemps at the Pilgrim Congregational Church in Brooklyn with Henry Ward Beecher in the pulpit, saboteurs in the congregation and Captain Butter in the privy.

Nevers' all-black and "apparently numberless" company of detectives infiltrates the white ruling class as easily as the New York City street gangs. Interesting black characters in fact swarm through American Falls. They add tremendous depth to the social background, and Batchelor has a good ear for Carolina dialects. Here, some former slaves comment on the fate of the Sea Island planters, providing an eloquent commentary on emancipation: "Big buckrah, dey gone where e'en Jesus ain' fetchin' dem back, no mo'."

The Rebel conspiracy to burn down New York fizzles out when the incendiary device proves defective. Afterward there is a manhunt, the thrilling climax of the novel. But many puzzles remain unsolved. After Lee's surender, Butter and Nevers try to figure out what really happened. "Was Colonel Baker a double agent, or a triple agent. Was he working for Oliphant? Or was Oliphant working for the same men Colonel Baker was working for? And who was Colonel Baker working for?"

The questions do pile up; the reader can frame his own answers. One thing is sure: entirely new aspects of the Civil War are explored in American Falls. Also: it is not a northern novel or a southern novel; it is a national novel. As Oliphant stands on New York's Battery, he senses the age's spirit: "I've often thought, standing here, that I was at the bow of a giant earthen ship called New-York. Blunt prow, bloated amidships, tapered aft, with her steam up from the chimneys and stacks fed by the coal bin of the markets. And she was heading out. Not into the Atlantic. Into the future."