Some wonder what we need the Book of Mormon for when we already have the Bible. I don't know all of the answers, and I don't always know the purpose behind everything that God does. What I do know is that I like to think logically when I am puzzled about something. As I have pondered this question my logic kicked in and helped me understand a little bit better.
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We read in the Bible in the Book of John when Christ is giving the parable of the Good Shepherd and the sheep, "And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd". (John 10:16) Here Jesus proclaims himself as the Good Shepherd and the sheep are his people. By saying other sheep not of this fold, he is talking about other people not of this land.
The Highlight of the Book of Mormon is when Christ appears in the Americas as a resurrected being and ministers to the people there. He gives an almost identical discourse to that known as the Sermon on the mount found in the Bible. He then explains to the people known as Nephites, "And verily I say unto you, that ye are they of whom I said: Other sheep I have which are not of this fold; them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd." (3 Ne 15:21)
The Book of Mormon is another witness of the Divinity and Sonship of Jesus Christ. As I have studied it alongside the Bible I have grown to learn, love, and apply its teachings in my own life and have been able to feel of God's individual love for me as one of his children.