Question: "Does the warning in Revelation 22:18-19 apply to the entire Bible or just the Book of Revelation?"
Answer: Revelation 22:18-19 contains a warning to anyone who tampers with the biblical text: “For I testify together to everyone who hears the Words of the prophecy of this Book: If anyone adds to these things, God will add on him the plagues that have been written in this Book. And if anyone takes away from the Words of the Book of this prophecy, God will take away his part out of the Book of Life, and out of the holy city, and from the things which have been written in this Book.” The question is whether these verses refer to the whole Bible or just the Book of Revelation.
This warning is given specifically to those who distort the message of the Book of Revelation. Jesus Himself is the Author of Revelation and the giver of the vision to the apostle John (Revelation 1:1). As such, He concludes the book with a confirmation of His testimony to the finality of the prophecies contained in Revelation. These are His words, and He warns against distorting them in any way, whether through additions, subtractions, falsifications, alterations, or intentional misinterpretations. The warning is explicit and dire. The plagues of Revelation will be visited upon anyone guilty of tampering in any way with the revelations in the book, and those who dare to do so will have no part in eternal life in heaven.
Although the warning in Revelation 22:18-19 is specific to the Book of Revelation, the principle applies to anyone who seeks to intentionally distort God's Word. Moses gave a similar warning in Deuteronomy 4:1-2, where he cautioned the Israelites that they must listen to and obey the commandments of the Lord, neither adding to nor taking away from His revealed Word. Proverbs 30:5-6 contains a similar admonition to anyone who would add to God’s words: he will be rebuked and proven to be a liar. Although the warning in Revelation 22:18-19 applies specifically to the Book of Revelation, its principle must be applied to the entire revealed Word of God. We must be careful to handle the Bible with care and reverence so as to not distort its message.