The Book of Mormon is the most correct book on Earth because it teaches the fulness of the Gospel of Jesus Christ. Every page in the Book of Mormon has at least one mention of the proper title of Deity in one form or another (God, Father, Lamb of God, Son of God, Holy One of Israel, etc.), with a total of 4,032 proper titles of Deity used throughout the book (not including the words "he", "his", "him", etc. It only includes the proper titles, meaning those capitalized). Moroni wrote of the purpose of the Book of Mormon. He said it is "to the convincing of the Jew and Gentile that JESUS IS THE CHRIST, the Eternal God, manifesting himself unto all nations" (Book of Mormon, Title Page).
Elder Jeffrey R. Holland of the Quorum of the Twelve taught, "Indeed, in its role of restoring plain and precious biblical truths that had been lost, while adding scores of new truths about Jesus Christ and preparing the way for the complete restoration of his gospel and the triumphant day of his millennial return, the Book of Mormon may be considered the most remarkable and important religious text ever given to the world” (Christ and the New Covenant, p. 9–10).
The reasons why the Book of Mormon is the most correct of any book on earth is simply that it teaches a fulness of the Gospel of Jesus Christ. President Ezra Taft Benson said, "If we really do our homework and approach the Book of Mormon doctrinally, we can expose the errors and find the truths to combat many of the current false theories and philosophies of men" (“Jesus Christ—Gifts and Expectations,” Ensign, Dec. 1988, p. 4).
Indeed, the Book of Mormon is the most correct of any book on the face of the Earth because the doctrines of Christ found within its pages anchor one to the Spirit of the Lord, and confirm correct teachings found within the Bible, while sifting out the false teachings of men, both in the world and within the Bible (which was translated by men, and not by a Prophet of God).
I know the Book of Mormon is the most correct of any book on earth because I have read it. I have studied it, comparing it meticulously with the Bible, and have found the teachings of the Bible are corroborated by the Book of Mormon, and the doctrines taught in the Bible are agreed upon by the Book of Mormon. To put it another way, if one has a plank of wood, and nails one end to the floor, the plank can still be turned about a full 360 degrees. However, nail both ends of the plank to the floor, and it is immoveable; such is the case with the Bible and Book of Mormon - they anchor each other and the doctrine of Christ to the floor of revelation, never to be moved. I know this is true, and all may know through study of the Book of Mormon, and a prayer to God to know of the veracity thereof. In the name of Jesus Christ, amen.