What does Revelation 22:18-19 mean? It says the same thing in Deuteronomy 4:2.
Revelation 22:18-19 means pretty much exactly what it says. However many have tried to twist it into something that it does not say. Lets take a look at it.
18 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:
19 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.
Now here is a very simple summary of it. If a man takes it upon himself to alter the revealed word of God he will be punished and not allowed into the kingdom of God. Its pretty simple really. And while it does explicitly say its for the Book of Revelation (or Deuteronomy as the case maybe) it does apply to all the revealed words of God.
Pretty simple yes? Here is what it does not say. It does not say that the revealed word can not have been altered. After all why give such a commandment if no one will be allowed to break it? People did alter it, which is why a restoration was needed. It also does not say that God can not speak further. Nothing in these verses gags God and says that he will/can not give more revealed words.