What is the Book of Mormon?
The Book of Mormon is a record of the peoples of the American continents from about 600 B.C. to 400 A.D. It begins with a group of people in the Jerusalem in Israel and traces their journey to the Americas. The Book of Mormon primarily consists of sermons, narratives, and histories. It is a collection of records much like the Bible. The Book of Mormon as a whole was put together by an ancient prophet-historian name Mormon (hence the title, The Book of Mormon).The climax of the record describes Jesus Christ visiting the people in the Americas.
And it came to pass, as they understood they cast their eyes up again towards heaven; and behold, they saw a Man descending out of heaven; and he was clothed in a white robe; and he came down and stood in the midst of them; and the eyes of the whole multitude were turned upon him, and they durst not open their mouths, even one to another, and wist not what it meant, for they thought it was an angel that had appeared unto them.
And it came to pass that he stretched forth his hand and spake unto the people, saying:
Behold, I am Jesus Christ, whom the prophets testified shall come into the world.
And behold, I am the light and the life of the world; and I have drunk out of that bitter cup which the Father hath given me, and have glorified the Father in taking upon me the sins of the world, in the which I have suffered the will of the Father in all things from the beginning. 
The Book of Mormon powerfully testifies of Christ and Christ’s atonement. Those who question the truthfulness of the record cannot deny that the book is Christ centered.
Where did the Book of Mormon come from?
According to Mormonism, the Book of Mormon is a translation from a record delivered to Joseph Smith. An angel named Moroni, who was also the final writer in the Book of Mormon, appeared to Joseph Smith and told Joseph where the record was hidden in a stone vault in New York, near the Smith farm. The record was engraved onto plates of gold. Mormons believe that Joseph translated the record, not through the traditional process of translation, but through the gift and power of God.
Why do we need the Book of Mormon?
Mormons believe that the Book of Mormon stands as evidence that God can and does continue to reveal his word in this age. Mormons believe that if the Book of Mormon is true, then Joseph Smith was a prophet. This is based on the assumption that the book could not have been translated by the unschooled boy in his early twenties, unless it was through some divine means.
The Book of Mormon also testifies powerfully of Jesus Christ. In this way it is another witness of Christ. Mormons believe this is important in this day and age when Christ’s name is defamed so prolifically.
Finally, Mormons believe that the Book of Mormon clarifies and explains the doctrines taught in the Bible: “in the mouth of two or three witnesses every word may be established.”  For this reason the Book of Mormon has immense value as a canon of doctrine.
Is the Book of Mormon true?
There is a great deal of scholarship both by Mormons and non-Mormons alike on the Book of Mormon. Both sides have struggled to find conclusive evidence one way or the other. But Mormons believe that the best way to know whether the Book of Mormon is true or not is to follow the exhortation extended at the end of the record by Moroni, one of the writers a prophets of the Book of Mormon:
Behold, I would exhort you that when ye shall read these things, if it be wisdom in God that ye should read them, that ye would remember how merciful the Lord hath been unto the children of men, from the creation of Adam even down until the time that ye shall receive these things, and ponder it in your hearts.
And when ye shall receive these things, I would exhort you that ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost.
And by the power of the Holy Ghost ye may know the truth of all things. 
Basically, Moroni testifies that God will tell you if the Book of Mormon is true or not if you simply pray and ask after having read in its pages. Millions of Mormons have testified that they have tested Moroni’s promise and discovered its veracity. Moroni’s promise is consistent with the teachings of the Bible: “ask and ye shall receive,”  “If any of you lack wisdom, let him ask of God,”  and “Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you ….”  This is convincing evidence that prayer is a means for obtaining truth. And Mormons believe that this is the best way to find out the truth about the Book of Mormon.
Try it. Take the challenge and find out for yourself.
 3 Nephi 11:8-11
 Matthew 18:16
 Moroni 10:3-5
 John 16:24
 James 1:5
 Matthew 7:7