Johnny Skeptic

Revelation 22:18-10 say "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 tampering with the texts were not possible, there would have been no need for the warnings.

Will someone please explain something to me? Regarding ".......God shall take away his part out of the book of life.......," does that not apply only to Christians, since skeptics do not have their names written in the book of life?