1. It's the Handbook for Turning to God.

"Mormon" refers to the place where people first chose God and formed the first church. The title "Book of Mormon" refers to the events of the location, not the person. See Name Of.

2. It is the Handbook for America - A Standard Unto My People.

Just as there have been promises made to the City of David, and the tribe of Judah, so too have there been promises made to the land of America, that God would use the Book of Mormon as a Standard for its people:

1 But behold, there shall be many—at that day when I shall proceed to do a marvelous work among them, that I may remember my covenants which I have made unto the children of men, that I may set my hand again the second time to recover my people, which are of the house of Israel;
2 And also, that I may remember the promises which I have made unto thee, Nephi, and also unto thy father, that I would remember your seed; and that the words of your seed should proceed forth out of my mouth unto your seed; and my words shall hiss forth unto the ends of the earth, for a standard unto my people, which are of the house of Israel; (2 Nephi 29:1-2)

 

Only the Book of Mormon details the destiny of this great nation; its promises and blessings; its mandate and God given stewardship over ALL NATIONS OF THE EARTH.

3. Restore Lost Doctrine.

Where are the plain instructions in the Bible for Baptism and Communion? They are nowhere to be found. For this reason the body of Christ has been divided, and for this reason has The Book of Mormon been given.

4. God will establish Every Doctrine in the Mouth of Two or More Witnesses. (2 Corinthians 13:1)

Where is God's Second Witness to the Bible? The Book of Mormon is God's Second Witness to the Bible:

a. For out of Jerusalem shall go forth a remnant, and they that escape out of mount Zion: the zeal of the LORD of hosts shall do this. (Isaiah 37:32)

 

b. And other sheep I have, which are not of this fold. (John 10:16)

 

c. And the vision of all is become unto you as the words of a book that is sealed. (Isaiah 29:11)

 

d. Wherefore murmur ye, because that ye shall receive more of my word? Know ye not that the testimony of two nations is a witness unto you that I am God, that I remember one nation like unto another? Wherefore, I speak the same words unto one nation like unto another. And when the two nations shall run together the testimony of the two nations shall run together also.
And I do this that I may prove unto many that I am the same yesterday, today, and forever; and that I speak forth my words according to mine own pleasure. And because that I have spoken one word ye need not suppose that I cannot speak another; for my work is not yet finished; neither shall it be until the end of man, neither from that time henceforth and forever. (2 Nephi 29:8-9)

5. To prove to the Jews that Jesus is The Christ.

God knew, and prophets foretold that the Jews would reject the Messiah. This is why God, in His infinite wisdom prepared a Second Witness - to help their unbelief.