The Importance of the Book of Mormon:

In first Nephi chapter 13 verses 40 and 41, an angel states to Nephi, "These last records [The Book of Mormon and other scriptures that have and will come forth] which thou has seen among the Gentiles, shall establish the truth of the first, [the Holy bible] which are of the twelve apostles of the Lamb, and shall make known the plain and precious things which have been taken away from them; and shall make known to all kindreds, tongues, and people, that the Lamb of God is the Son of the Eternal Father, and the Savior of the world; and that all men must come unto him, or they cannot be saved. And they must come according to the words which shall be established by the mouth of the Lamb; and the words of the Lamb shall be made known in the records of thy seed, as well as in the records of the twelve apostles of the Lamb; wherefore they both shall be established in one; for there is one God and one Shepherd over all the earth."

I find another scripture valuable in 1 Nephi 15:24 where Nephi says to his brethren and to all of us, "And I said unto them that it was the word of God, and whoso would hearken unto the word of God, and would hold fast unto it, they would never perish; neither could the temptations and the fiery darts of the adversary overpower them unto blindness, to lead them away to destruction. Wherefore, I, Nephi, did exhort them to give heed unto the word of the Lord; yea, I did exhort them with all the energies of my soul, and with all the faculty which I possessed, that they would give heed to the word of God and remember to keep his commandments always in all things."