SHADOW CATCHER. By Charles Fergus, Soho Press, 308 pp., $19.95THIS is a sometimes confusing but always fascinating novel. It is confusing at first because you don't know whether it's fact or fiction, and the facts seem stranger than fiction. The novel's factual base is a groundbreaking ceremony on Feb. 22, 1913, with President William Howard Taft wielding the shovel, for a huge museum and statue memorial to be built at the tip of Staten Island to honor the vanishing Indian. Members of 11 Indian tribes sign a Declaration of Allegiance to the government that is hastening their demise, while the band plays the national anthem, and newly minted Indian-head buffalo nickels are handed out. The factual vehicle that carries the novel along is the Rodman Wanamaker Expedition to the North American Indian - a private railroad car taken to 90 tribes on more than 60 reservations. Its purpose is to persuade the tribes that have not yet vanished to pledge their allegiance and to collect photographs and artifacts for the planned memorial in the New York harbor. What an array of characters the Pullman car carries! Dr. Joseph Dixon, disgraced former Baptist minister, now educational director for the Wanamaker department stores, an accomplished orator and slick con man, is an actual historical character. The hefty photographer, Benny Booth, a bully, is fictitious. The portraits he takes are of Indians carefully posed, with expressionless faces. The Washington Dispatch newspaper, however, shows another kind of photo, unposed and untouched: A picture of a small Indian boy with a bloated belly standing in front of a shack with a splintered door. A landscape of another village, a shanty town standing among piles of cans and garbage. No captions, no credit lines. Nothing to indicate where they were taken; such scenes were common throughout the country. The commissioner of Indian Affairs in Washington and Rodman Wanamaker in New York are furious. Who is taking these damning shots? James McLaughlin doesn't know. At 71, he is the oldest member of the Expedition, a loyal, brainwashed agent of the Bureau of Indian Affairs. He commanded the tribal police who killed the revered Sioux Chief Sitting Bull in 1890. Something about this preys on his mind. Mclaughlin, who is based on an actual person, had five children. He adopted Emma Crow King, the daughter of one of Sitting Bull's chiefs. In the novel, she is depicted as Annie Owns the Fire, a fictional character, who is dismissed as a tea cher for describing to her young pupils the sacred Sun Dance prohibited by the Indian Bureau. Ansel Fry is a young Indian Bureau stenographer assigned to McLaughlin. He is at once the fictional traitor and hero of the Expedition. Fry carries hidden in his vest a small, secret camera with which he takes the candid shots. So through the land of the vanishing Indian, the Wanamaker Expedition wends its unlovely way. Its members see El Tovar, "the holiest American shrine" , and ride muleback down into the Grand Canyon. At Ganado on the great Navajo Reservation, in Lorenzo Hubbell's Trading Post, they spend the night listening to Hubbell's stories. At the site of the Little Big Horn battle, the party views Gen. George Armstrong Custer's grave, but Fergus wisely refrains from entering the continuing controversy about him. Yet the site of the Custer massacre brings out McLaughlin's opinion about Sitting Bull, the equally famous Hunkpapa Sioux chief and medicine man. "When Reno attacked and the rifle balls started ripping through the tipis [tepees], Sitting Bull gathered up his wives and children and lit out for the hills," he relates. "After the battle, they sent out riders and overtook him 10 miles from camp. Later, he explained it away by saying that his capture would have meant the loss of his medicine to the Sioux." He stops, then bursts out, "A coward! A liar! An egotist! A fraud! All the faults of the red man and none of the virtues." Toward the end of the Expedition the narrative reads more like a novel. All the subplots unravel in dramatic personal confrontations. Annie Owns the Fire has been teaching at a tuberculosis sanitarium for Indian children. Yet even here the rule against children speaking their own language and speaking of ceremonies is harshly enforced. She joins company with the Expedition and things start to happen. Indians used to call the magic black boxes they believed would steal their souls "shadow catchers." This novel itself is the candid camera, the shadow catcher that catches the dark spirit of America in the era when it neglected its first Americans, forerunners of today's proud native Americans. The actual Wanamaker Expedition ended in December 1913 where ground had been broken for the Indian memorial 10 months before. It was never built. The United States was about to be drawn into World War I.