The Lord declared that in the last days, "many of the Gentiles shall say: ... A Bible, we have got a Bible, and we need no more Bible.' Have ye obtained a Bible save it were by the Jews? Know ye not that there are more nations than one? Know ye not that I, the Lord your God, have created all men, and that I remember those who are upon the isles of the sea; and that I rule in the heavens above and in the earth beneath; and I bring forth my word unto the children of men, yea, even upon all the nations of the earth? 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. Wherefore, because that ye have a Bible ye need not suppose that it contains all my words; neither need ye suppose that I have not caused more to be written. For I command all men, both in the east and in the west, and in the north, and in the south, and in the islands of the sea, that they shall write the words which I speak unto them." 2 Ne. 29:3,6-11 And there are also many other things which Jesus did, the which, if they should be written every one, I suppose that even the world itself could not contain the books that should be written. John 21:25
From the days of Adam, Christ has taught his gospel to his followers and they have kept records. It is because of these records that we have the Bible, which is a record kept by the Jews up through the time of Christ and his apostles. Many people in many lands have kept records of their dealings with God and their experiences living his gospel; however, outside of the works contained in the Bible, few of these other writings are available to us. One is. It is sometimes called the Stick of Joseph. Ezek 37:16-20
Christ's followers in the ancient Americas kept such a record. In about 400 A. D. the prophet Mormon made an abridgment of these records (hence the name Book of Mormon), engraving it on thin sheets of gold. His son, Moroni, completed the work and was instructed to seal up the record to come forth in the Lord's time.
It is this same Moroni who was sent by God to inform Joseph Smith of the existence and location of the record. (We believe that angels are men, children of God, --either pre-mortal or post-mortal spirits, or resurrected men-- who are sent from the presence of God to to earth to teach and bless mortal men.) Joseph Smith was taught by Moroni and, after a few years, allowed to take and translate the record. Besides Joseph, several other men saw and handled the plates and bore testimony of their existence. Three men were shown the plates by an angel of God and were instructed to bear witness that were translated by the gift and power of God. Though they became disaffected with the church and some never returned, they never denied that an angel showed them the plates from which the Book of Mormon was translated.
The Bible is a record of Christ's followers in Jerusalem. The Book of Mormon is a record of Christ's followers in America. The Bible is the word of God and testifies that Jesus is the Christ. The Book of Mormon establishes the truth of the Bible and adds another witness of the divinity and mission of Jesus Christ. For behold, [the Book of Mormon] is written for the intent that ye may believe [the Bible]. Mormon 7:9
The Book of Mormon tells the story of a Jewish prophet and his family who were warned to leave Jerusalem before its destruction c.600 B.C. and were brought to the Americas. It describes the religious and secular history of the great civilization they founded here. It contains quotes and references to the scriptures that were brought from Jerusalem, particularly Isaiah, and preserves the teachings of the prophets in the new world. It tells of Christ's visit to these 'other sheep' after his resurrection. The story is also told of a family spared from the curse at the time of the tower of Babel and brought by God to this land, and of another group that was brought here, led by Mulek, the surviving son of the Old Testament king Zedekiah.
The Book of Mormon teaches that Jesus Christ is the Savior of the world. It teaches the purposes of the law of Moses, which was observed by the Book of Mormon peoples before the coming of Christ; and it exhorts everyone who reads it to look to Christ for salvation. It agrees with and reinforces Bible teachings and presents the gospel of Jesus Christ with great clarity. The Book of Mormon is full of many wonderful, inspiring, and faith-promoting stories and teachings. There are so many great stories, it is hard to choose a favorite. One of the most touching stories is of Christ's visit to the Nephite people (3 Ne. 11) after his resurrection and following the great destruction that occurred at the time of his death (3Ne. 8). It is a beautiful account of Christ's experiences teaching a people who loved and accepted him. You can feel the great love that He had for them.
Moroni knew that the Book of Mormon would come forth in a time when it would be very difficult for people to believe it. As a prophet of God, he issued this promise: 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. Moroni 10:4-5
I believe that the Book of Mormon is truly the word of God, but you should not believe it because I say it is, nor should you disbelieve it because someone else tells you it isn't. If you really want to know whether or not it is from God, read it, ask God, and know for yourself. God cannot lie and he will not mislead you.