Aside from the Book of Mormon not containing the so-called “precious truths” that were allegedly lost, of LDS essential doctrines (e.g., LDS polytheism [i.e., the idea that many true Gods exists, technically, henotheism], Exaltation, Eternal Progression, the idea of Aaronic and Melchizedek priesthoods, sealing, eternal marriage et al.), the LDS doctrine has always rejected the biblical revelation of Christ.        

In spite of who authored it, the Book of Mormon contains significant contradictions both historical and theological (and logical). Of the abounding material objectively demonstrating this (from its inception in 1830), we have documented a vast amount of erroneous teaching contained in the LDS so-called scriptures (i.e., the Book of Mormon, Doctrine and Covenants, and Pearl of Great Price).

Also, my friends at Institute for Religious Research have provided a simple short article, Seven Contradictions Between The Book of Mormon and the Bible. Although, as pointed out above, many of the fundamental heresies of the LDS Church such as polytheism and Exaltation, which are post-Book of Mormon, this article addresses seven significant false LDS doctrines, which are in fact currently contained in the Book of Mormon.

In fact, it is easily proven that Smith’s early teachings as contained in the Book of Mormon (and early sections of D&C) controvert present- day LDS theology on many accounts. See Early Teachings of Joseph Smith and the Book of Mormon, which Contradict Present- day LDS Theology – See Early Teachings of Joseph Smith.

Although there are many more contradictions and factual errors in the Book of Mormon (and in the other LDS scripture) than seven, they sufficiently and objectively demonstrate that the Book of Mormon is untrustworthy patently contradicting God’s revelation contained in the biblical content. See our expanded article on the Book of Mormon here Book of Mormon

Note, Aside from the seven contradictions briefly listed below by IRR (and many others can be shown), one additional Book of Mormon false teaching is its repeated affirmation of Modalism, that is,  Oneness theology – see Modalism and the Book of Mormon 

IRR article:

There are many serious objections to the claim of Joseph Smith and the LDS church that the Book of Mormon is divinely inspired Latter-day scripture supplemental to the Bible.* However, none are more significant than the numerous contradictions between Book of Mormon teaching and the Bible. This list is illustrative only, not exhaustive.

(1) The Book of Mormon teaches that little children are not capable of sin because they do not have a sinful nature (Moroni 8:8). In contrast, the Bible in Psalm 51:5 clearly teaches that we have a sinful nature from birth: “Surely I was sinful at birth, sinful from the time my mother conceived me” (NIV). (This does not mean that those who die in infancy are lost.**)

(2) The Book of Mormon teaches that the disobedience of Adam and Eve in eating the forbidden fruit was necessary so that they could have children and bring joy to mankind (2 Nephi 2:23-25). In contrast, the Bible specifically declares that Adam’s transgression was a sinful act of rebellion that unleashed the power of sin and death in God’s perfect world (Romans 5:12; 8:20-21). There is no Biblical support for the view that Adam and Eve could only fulfill the command to “be fruitful and multiply” (Genesis 1:28) by disobeying God’s command regarding the forbidden fruit (Genesis 2:17). The Book of Mormon teaching that these divine commands are contradictory, and that God expected Adam and Eve to figure out that in reality He wanted them to break the latter command (“of the tree of the knowledge of good and evil, thou shalt not eat of it”) in order to keep the former (“be fruitful and multiply”), has no basis in logic or the Biblical text, and attributes equivocation to God.

(3) The Book of Mormon teaches that black skin is a sign of God’s curse, so that white-skinned people are considered morally and spiritually superior to black-skinned people (2 Nephi 5:21). In contrast, the Bible teaches that God “made of one blood all nations of men” (Acts 17:26, KJV), that in Christ distinctions of ethnicity, gender and social class are erased (Galatians 3:28), and that God condemns favoritism (James 2:1). [NOTE: See our article, Mormonism and Black Skin, for an documented and expanded look at the LDS views both delineated in the LDS scriptures and by way of sermon or statements by LDS General Authorities (LDS Presidents, Apostles, etc.) regarding people with dark skin, which the LDS has seen, for almost 200 years, as “cursed”].      

(4) The Book of Mormon teaches that, “it is by grace that we are saved, after all we can do” (2 Nephi 25:23; see also Moroni 10:32). In contrast, the Bible teaches that apart from Christ we are dead in sin (Ephesians 2:1,5) and unable to do anything to merit forgiveness and eternal life. Salvation is wholly of grace (Ephesians 2:8-9; Romans 11:6; Titus 3:5-6), not by grace plus works. Good works are a result, not the basis, of a right relationship with God (Ephesians 2:10).

(5) According to the Book of Mormon, about 600 years before Christ, a Nephite prophet predicted that “many plain and precious parts” (1 Nephi 13:26-28) would be removed from the Bible. In contrast, from the Bible it is clear that during His earthly ministry, Jesus himself constantly quoted from the Old Testament Scriptures, and showed full confidence in their completeness and accurate transmission as they had survived down to His time. Jesus declared that “heaven and earth shall pass away, but my words shall not pass away” (Mark 13:31; see also Matthew 5:18), and promised His disciples who were to pen the New Testament that the Holy Ghost “shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you” (John 14:26); Jesus further promised the apostles that they would “bring forth fruit, and that your fruit should remain” (John 15:16). These promises clearly imply that the fruit of the apostles — the New Testament Scriptures and the Christian church — would endure.

(6) According to a Book of Mormon prophecy (Helaman 14:27), at the time of Christ’s crucifixion “darkness should cover the face of the whole earth for the space of three days.” In contrast, the New Testament gospel accounts declare repeatedly that there was darkness for only three hours while Jesus was on the cross (Matthew 27:45; Mark 15:33; Luke 23:24).

(7) The Book of Mormon teaches that there were many high priests serving at the same time (Mosiah 11:11; Alma 13:9-10; 46:6,38; Helaman 3:25) among the Book of Mormon people who are described as Jewish immigrants from ancient Israel who “kept the law of Moses” (e.g., 2 Nephi 25:10; Jacob 4:5; Jarom 1:5). In contrast, it is clear from the Bible that only one individual at a time occupied the office of high priest under the Old Testament dispensation (see, for example Leviticus 21:10; Matthew 26:3; Hebrews 8:6-7). (The mention in Luke 3:2 of “Annas and Caiaphas being the high priests” is not a real exception — in Christ’s time Israel was under the domination of the Romans, who intervened to change the high priest at will. See John 18:13, which describes Annas as “father-in-law to Caiaphas, which was the high priest that same year.”)

CONCLUSION: The contradictions between the Book of Mormon and the Bible constitute a most serious obstacle to accepting the Book of Mormon as Latter-day scripture supplemental to the Bible. The Bible came first, not the Book of Mormon. And whereas the Bible is organically linked to the earthly ministry of Jesus Christ by extensive surviving manuscript evidence going back as far as A.D. 125-30, the Book of Mormon is wholly lacking in any such evidences of ancient origin. Is it not reasonable, therefore, to make the Bible the standard for judging the Book of Mormon, and not the other way around? If we accept the Bible as our “measuring stick” for spiritual truth, the Book of Mormon must be rejected.