B. H. Roberts says the Book of Mormon is "a new witness for God" to the Latter-day Saints.
B. H. Roberts, Speech, "A New Outlook Upon Mormonism," 1924, rep. in "His Final Decade: Statements about the Book of Mormon, B. H. Roberts," Foundation for Ancient Research and Mormon Studies, circa 1985
Following its bold and unique initiative, "Mormonism" announced a revelation respecting America and her ancient inhabitants that was equally astounding and appealing. Who were these people of the western world discovered with their continent four hundred years ago? Were they children of the Most High? And if so had God left himself without witnesses among them? To this question men could give no answer. But "Mormonism" did by producing an American volume of scripture written and compiled by their prophets, proclaiming not only an Israelitish origin for the people, but giving an account of the resurrected Christ's personal visit to them, after his departure from Judea; also the proclamation of the one and "Everlasting Gospel" to them by the Christ; the founding of a church; and at the necessary departure of the Son of God from their midst, a promise given of a future return, and a personal reign with the righteous in a Kingdom of Glory. If all this were not true, it might well be hoped that it was true, for it should say so much in vindication of the justice of God in not allowing whole continents of people to perish in ignorance of God's plan of human salvation. It would add so much to the vision of a loving Christ, this visit to the people of America, and the establishment of his Gospel and his church among them. It would mean so much to the present distraught Christendom if a New Witness could be found in the voice of the sleeping nations of ancient America, testifying to the Deity of the Christ; to the reality of the resurrection from the dead, and the life everlasting. To the Latter-day Saint this is what the Book of Mormon is, A New Witness for God, and for the fundamental truths of the old Christian faith. This is what it does for him: strengthens his faith, but increasing the evidence on which that faith rests; makes brighter his star of hope of the life everlasting; his church, rising out of all this, and guided by continuous revelation,—abiding in touch with God—becomes for him a present temple of God, built up of living stones wherein is not darkness or doubt.