Critics argue that The Book of Mormon cannot be true because its very existence contradicts what is stated in the Holy Bible in Revelation 22:18-19:
For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book: and if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
If this one verse of scripture can be used to speak of the entirety of the Bible – from Genesis to Revelation – and be interpreted to mean that no one is permitted to “add to” or “take away” from the words that are written in the book (the Bible), then could it not follow that a verse found in the Old Testament Book of Deuteronomy would have similar interpretation? In Deuteronomy 4:2 are recorded these words:
Ye shall not add unto the word which I command you, neither shall ye diminish ought from it, that ye may keep the commandments of the Lord your God which I command you.
From this single verse one could purport that there should be no more scripture after the first five books of the Bible (or the books of Moses, also known as the Pentateuch) – Genesis, Exodus, Leviticus, Numbers, and Deuteronomy. However, many biblical scholars would agree that this is not the case. Just as this verse found in the Old Testament of the Bible does not speak of the entirety of the Holy Writ, the aforementioned verses quoted from the Book of Revelation in the New Testament do not speak of the entirety of the Holy Writ either.
First, and foremost, critics fail to realize that the Bible as presented today, is not in chronological order. Simply stated, while the Book of Revelation may be the last book contained in the Bible, it was not the last book of the Bible written.
Evidence indicates that 1 John and Jude were written up to 20 years later than Revelation, which is believed to have been written about 90 AD. Many also believe that the Gospel of St. John was written after the Book of Revelation.
Critics seem to forget that the Bible is a collection of books. John’s Book of Revelation was a single book for centuries before it was assembled with other books to form the Bible. How can critics say revelation 22 refers to the entire Bible when there was no Bible when Revelation was written, and there would not be one for hundreds of years? (Stephen R. Gibson, One Minute Answers to Anti-Mormon Questions, pg. 48-49
With that in mind, most biblical scholars will agree that the book that is referred to when the scripture in the Book of Revelation says “the prophecy of this book”, is indeed the Book of Revelation, and not the entire Bible. Members of The Church of Jesus Christ of Latter-day Saints believe that God’s Word nebver ceases. Therefore, as stated by Stephen R. Gibson, author of One Minute Answers to Anti-Mormon Questions:
While Rev. 22:18, 19 forbids man from adding to “the prophecy of this book” [the Book of Revelation], it in no way prevents God or his son, Jesus Christ, from giving additional revelation to man through his prophets.
The critics misuse Revelation, misunderstand the process by which the Bible canon was formed, and must ignore other, earlier scriptures to maintain their position. Their use of this argument is a form of begging the question whereby they presume at the outset that the Book of Mormon and other scriptures are not the Word of God, which is precisely the point under debate. In its proper context, the passage in Revelation actually supports the teachings of the Book of Mormon that many plain and precious things would be taken away from the Bible. It also shows clearly the need for another book of scripture like the Book of Mormon to restore those lost and sacred teachings. If the Book of Mormon and other modern scriptures are the work of uninspired men or the arm of flesh, then of course one ought not to trust them. If, however, they are indeed the word of the Lord to prophets, then all who desire to be saved ought to carefully heed them. 
Critics seem to ignore the following: 
- The book of Revelation was written prior to some of the other biblical books, and prior the Bible being assembled into a collection of texts. Therefore, this verse can only apply to the Book of Revelation, and not the Bible as a whole (some of which was unwritten and none of which was yet assembled together into ‘the Bible’). While the traditional date of the book of Revelation is A.D. 95 or 96 (primarily based on a statement by Irenaeus), many scholars now date it as early as A.D. 68 or 69. The Gospel of John is generally dated A.D. 95-100.
- The New Testament is made up of first the four Gospels and then second the epistles of the apostles. Since the book of Revelation is neither a gospel nor an epistle, it was placed at the end of the canon in its own category. Therefore, John cannot have intended the last few sentences of Revelation to apply to the entire Bible, since he was not writing a ‘final chapter’ for the New Testament and since the Bible would not be completed and canonized for some centuries later.
- Other scriptures (such as Deuteronomy 4:2, Deuteronomy 12:32, and Proverbs 30:6) likewise forbid additions; were the critics’ arguments to be self-consistent, they would have to then discard everything in the New Testament and much of the Old, since these verses predate “other scripture” added by God through later prophets.
- Further evidence that Rev. 22:19 is not referring to the entire bible when it reads “words of the book of this prophecy” is found if one reads Revelation 1:3,11:
Blessed is he that readeth, and they that hear the words of this prophecy, and keep those things which are written therein: for the time is at hand…Saying, I am Alpha and Omega, the first and the last: and, What thou seest, write in a book, and send [it] unto the seven churches which are in Asia; unto Ephesus, and unto Smyrna, and unto Pergamos, and unto Thyatira, and unto Sardis, and unto Philadelphia, and unto Laodicea.
- It is self evident that the book referred to at the very beginning of Revelation is the same book being referred to at the very end of Revelation. Everything that John saw and heard in between these two statements are the contents of that book.
- Even if the passage in Revelation meant that no man could add to scripture; it does not forbid that God may, through a prophet, add to the Word of God. If this were not possible, then the Bible could never have come into existence.
The Apostle Peter tells us that prophecy comes as holy men of God speak as they are moved by the Holy Ghost (2 Pet. 1:21). As holy men write, these things become scripture. The Church of Jesus Christ of Latter-day Saints agrees with the Lord, as recorded in John 16:12, that Christ has more to reveal to us and that he does it through holy men of God as moved upon by the Holy Ghost (D & C 68:4), and that the result is scripture after it is accepted and canonized by the Church. Thank goodness for a Church that teaches that God still loves us enough to reveal His word to us in our day. (Stephen R. Gibson, One Minute Answers to Anti-Mormon Questions, pg. 48-49)
The ancient Book of Mormon prophet Nephi understood how critics would respond to the Book of Mormon. His answer for the critics is thus:
Yea, wo be unto him that hearkeneth unto the precepts of men, and denieth the power of God, and the gift of the Holy Ghost! Yea, wo be unto him that saith: We have received, and we need no more! And in fine, wo unto all those who tremble, and are angry because of the truth of God! For behold, he that is built upon the rock receiveth it with gladness; and he that is built upon a sandy foundation trembleth lest he shall fall. Wo be unto him that shall say: We have received the word of God, and we need no more of the word of God, for we have enough! For behold, thus saith the Lord God: I will give unto the children of men line upon line, precept upon precept, here a little and there a little; and blessed are those who hearken unto my precepts, and lend an ear unto my counsel, for they shall learn wisdom; for unto him that receiveth I will give more; and from them that shall say, We have enough, from them shall be taken away even that which they have. Cursed is he that putteth his trust in man, or maketh flesh his arm, or shall hearken unto the precepts of men, save their precepts shall be given by the power of the Holy Ghost (2 Nephi 28: 26-31.)
- Additional Resources:
- The Bible in Mormonism
- Mormon Scriptures