Original: Church members officially regard the Book of Mormon as the "most correct" book of scripture, in that "a man would get nearer to God by abiding by its precepts, than any other book." This is, in part, because church members believe the Bible was the result of a multiple-step translation process and the Book of Mormon was not.
Simplified: The Book of Mormon is a book that Latter Day Saints believe is the word of God along with the Bible.