ORAL ROBERTS; An American Life. By David Edwin Harrell Jr. Indiana University Press. 622 pp. $24.95.

WHEN VISITORS arrive at the top tourist attraction in Tulsa, Oklahoma, they begin their tour at the foot -- or more properly, the wrists -- of the world's largest bronze sculpture, a 10-story rendering of a pair of hands clasped in prayer. They gaze upon a futuristic, 200-foot-tall prayer tower topped by an eternal gas flame, proceed along a 777-foot-long artificial stream called the River of Life, and wind up at an exhibit called "The Journey," a series of six dioramas depicting the life and times of the world's most famous faith healer. This popular attraction is not, as one wag has suggested, a theme park called Six Flags Over Jesus, but the showplace of the religious empire built by Oral Granville Roberts, preacher, healer, TV star and fund-raiser extraordinaire.

It makes a remarkable diorama exhibit and a remarkable story, the life of this tubercular stutterer, part Cherokee, part Sooner, who overcame his handicaps to become one of the most popular religious leaders in American history. And yet David Edwin Harrell Jr., Roberts' biographer, begins Oral Roberts: An American Life, on the defensive. "Oral Roberts has been one of the most influential religious leaders in the world in the twentieth century," he ventures, then fudges, "such judgments are risky and subjective at best," as though anticipating that his assertion might be met with a snort of incredulity by a body of scholars concerned with more serious religious matters.

The problem is that Roberts has built his empire on certain premises and promises that place him outside the mainstream of Protestantism and outside the mainstream of American life. He began his career as a raw, dirt-poor, revival-tent spellbinder, an itinerant, tongue- speaking preacher ordained by the Pentecostal Holiness Church. As a pentecostal, he believed in the "baptism of the Holy Spirit" -- that present-day Christians could recapture the miraculous powers ascribed to the disciples of Jesus in the Biblical Book of Acts, the power to heal and to prophesy and to speak in tongues. Roberts discovered that he possessed a hot, healing right hand that appeared to cause miraculous cures in afflicted believers, and his portable tent began to fill up with dozens and then hundreds of the blind, the deaf, the crippled, the cancerous.

Pentecostals, however, had long been regarded by other Protestants as a kind of outer Holy Roller fringe. And it was a small, poor denomination. Even before he was 30, Roberts, as Harrell notes, "was quickly outrunning the capacity of his church to reward him." In a quest for greater visibility and acceptance, he founded a university with a good basketball team, joined the Methodist Church, and became a pioneer in religious broadcasting, sending his message over the airwaves with such guest stars as Jerry Lewis, Robert Goulet, Minnie Pearl, and Tennessee Ernie Ford. Roberts, who had little patience for the grim, tragic side of Christianity, had cast away the notion that "you had to be poor to be a Christian" and had begun to explore the possibilities of positive thinking and prosperity in connection with faith. "Something good is going to happen to you!" he promised his viewers.

Roberts' rise to fame and fortune, however, has been clouded with controversy, from allegations by physicians of bogus healings, by theologians of feel-good religion, by the NCAA of unethical recruiting techniques at the university. Perhaps the greatest barrage of criticism was inspired by Roberts' claim, after experiencing financing difficulties with his new City of Faith hospital, that a 900-foot Jesus had appeared to him in a dream-vision, ordering that the project be completed.

Unfortunately, although Oral Roberts: An American Life is not an "authorized" biography, Harrell's attitude toward his complex, charismatic subject maintains the respectful restraint often present in a commissioned life story. Undoubtedly he conducted his research with both the thoroughness and objectivity of the professional historian. But at some point along the line, one feels, Harrell was transformed from reporter to semi-apologist. When he includes attacks on Roberts by journalists or other religious figures, he often takes it upon himself to defend Roberts. And in the case of Jerry Sholes, a disgruntled ex-employe of Roberts who wrote a scathing expos,e in 1979, Harrell merely mentions that the book was damaging to Roberts. One must turn to Sholes' book to find accounts of the inner-workings of Roberts' organization, including fund-raising techniques that promised individual prayers and attention to contributors, but which actually involved Roberts saying a prayer over computer printouts.

Only at the end of the book, in a section called "Meanings," does Harrell deal with the complexities of Roberts' character -- which include a habitual irritability and a bad temper. One loyal employe told Harrell that Roberts was a tough employer: "Figuratively speaking, he would emasculate you." Harrell, however, seems to feel that dealing with the implications of Roberts' flaws and failings would be tantamount to denigrating the importance of his own project. But a person need not be a saint in order to become a religious figure of great significance.

One is always reluctant, in religious matters, to be the one to cast the first stone, or even the third or fourth; how can a biographer evaluate a religious leader's claims to divine inspiration? Surely a person's congress with God falls into the category of privileged information. And so when preachers lik Oral Roberts or Jerry Falwell or Pat Robertson claim that they do the things they do because God tells them to, it becomes difficult to get through all the prophetic ink to the man. But perhaps Harrell might have used that ancient Biblical test of sincerity: "By their fruits shall ye know them." In the case of Oral Roberts, he has accrued a remarkable series of achievements and monuments by which he might be judged: a winning basketball team recruited by less- than-ethical means; a half-empty hospital that merges faith, hope, and technology; and a sprawling, multi- towered City of Faith with a facade that glitters like gold.