William J. Whalen summarizes the arguments for the Book of Mormon's dependence on View of the Hebrews; says the evidence is inconclusive.
William J. Whalen, The Latter-day Saints in the Modern Day World (New York: The John Day Company, 1964), 39, 54
Another theory suggests that Smith stole his ideas from a manuscript written by the Reverend Ethan Smith, a Congregationalist minister of Poultney, Vermont. Ethan Smith's book, Views of the Hebrews: or the Ten Tribes of Israel in America, was published in 1823 and attempted to solve the problem of the origin of the American Indians by offering a theory of their Jewish ancestry. This book was widely read and commented upon five years before the appearance of the Book of Mormon. Some think that Ethan Smith was working on a companion volume which somehow got into Joseph Smith's hands and formed the basis for the Book of Mormon. This theory remains even more speculative than the Spaulding theory. That Ethan Smith's ideas find many parallels in the Book of Mormon is undeniable and there is every likelihood that the Smith family had access to a copy of Views of the Hebrews or to abridgments which appeared in a number of weekly newspapers.
. . .
Doubters can only conjecture how this remarkable book was written. The available evidence does not permit a flat assertion that it was plagiarized from a manuscript by Spaulding or Ethan Smith or Rigdon. There are too many missing links which will probably never be found. The non-Mormon can, however, examine the contents of the book, especially the contents of the original 1830 edition, and arrive at the conclusion that the Book of Mormon was clearly the product of a writer in early nineteenth-century America rather than a collection of ancient records miraculously translated from Reformed Egyptian.