Mormons— or members of The Church of Jesus Christ of Latter-day Saints, sometimes inadvertently called the Mormon Church— “believe the Bible to be the word of God as far as it is translated correctly” (the eighth Article of Faith, one of 13 points of belief that outline the basic teachings and ordinances of The Church of Jesus Christ). The eighth Article of Faith continues: “We also believe the Book of Mormon to be the word of God.” The Book of Mormon is another testament of Jesus Christ, a companion scripture to the Holy Bible and a record of the peoples in ancient America and God’s dealings with them. It is not coincidence that the eighth tenet of Latter-day Saint beliefs mentions these two books of scripture. They are companion texts in witnessing of the Savior, Jesus Christ.
We delight in the knowledge of the Lord that we find recorded in the Old and New Testaments. We know that Jehovah of the Old Testament and Jesus of the New Testament are one and the same. We are grateful that this sacred record of God’s dealings with the people of ancient Israel and of His mortal ministry has been preserved and passed to us to enlighten our minds and strengthen our spirits. The fragmentary nature of the biblical record and the errors in it, resulting from multiple transcriptions, translations, and interpretations, do not diminish our belief in it as the word of God ‘as far as it is translated correctly.’ We read and study the Bible, we teach and preach from it, and we strive to live according to the eternal truths it contains. We love this collection of holy writ. 
Two Witnesses of the Savior
The Bible says, “In the mouth of two or three witnesses shall every word be established” (2 Corinthians 13:1). Webster’s New World College Dictionary defines “witness” as “an attesting of a fact; evidence; testimony.” Elder Russell M. Nelson, a member of the Quorum of the Twelve Apostles, applied this to scripture: “This assures God’s children that divine doctrines are confirmed by more than one scriptural witness.”  Members of The Church of Jesus Christ believe that the Book of Mormon is the second scriptural witness to the Bible.
Of the Book of Mormon, Elder Wirthlin said:
“‘We also believe the Book of Mormon to be the word of God.’ It is Another Testament of Jesus Christ, written ‘by way of commandment, and also by the spirit of prophecy and of revelation … to the convincing of [all people] that JESUS is the CHRIST, the ETERNAL GOD, manifesting himself unto all nations’ (Title Page, Book of Mormon). God brought forth the Book of Mormon as a second witness that corroborates and strengthens the Bible’s testimony of the Savior. The Book of Mormon does not supplant the Bible. It expands, extends, clarifies, and amplifies our knowledge of the Savior. Surely, this second witness should be cause for great rejoicing by all Christians.” 
Elder Nelson said:
“The Bible and the Book of Mormon are both witnesses of Jesus Christ. They teach that He is the Son of God, that He lived an exemplary life, that He atoned for all mankind, that He died upon the cross and rose again as the resurrected Lord. They teach that He is the Savior of the world. Scriptural witnesses authenticate each other. This concept was explained long ago when a prophet wrote that the Book of Mormon was ‘written for the intent that ye may believe [the Bible]; and if ye believe [the Bible] ye will believe [the Book of Mormon] also’ (Mormon 7:9). Each book refers to the other. … Love for the Book of Mormon expands one’s love for the Bible and vice versa.” 
The Bible and Book of Mormon Don’t Compete—They Complement Each Other
To highlight the complementary nature of the Bible and the Book of Mormon, Elder L. Tom Perry, a member of the Quorum of the Twelve Apostles, quotes the ancient prophet Nephi, whose writings are found in the Book of Mormon. Elder Perry said:
“Why is it important for the world to have both the Bible and the Book of Mormon? I believe the answer is found in the 13th chapter of 1 Nephi. Nephi records: ‘And the angel spake unto me, saying: These last records, which thou hast seen among the Gentiles [the Book of Mormon], shall establish the truth of the first [the 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’ (verse 40).
“Neither the Bible nor the Book of Mormon in and of themselves is sufficient. Both are necessary for us to teach and learn about the full and complete doctrine of Christ. The need for the other does not diminish either one of them. Both the Bible and the Book of Mormon are necessary for our salvation and exaltation. As [past LDS Church] President Ezra Taft Benson so powerfully taught, ‘When used together, the Bible and the Book of Mormon confound false doctrines’ (‘A New Witness for Christ,’ Ensign, Nov. 1984, 8).” 
In and of itself, the Bible is not perfect. But combined with the Book of Mormon, both scriptural texts are powerful witnesses of the Savior, Jesus Christ, and God’s plan for His children.