John Piper writes about being blotted out of the Book of Life:
Being in the book keeps you from doing what would get you erased from the book if you did it.
Notice the inherently tautological nature of this statement. If John, of Revelation, believed as much, why did he not state it? Why did he state it in the way he does, where there is a natural tendency to conclude losing your place in the Book of Life was possible?
And why does Piper ignore the very last warning in the book of Revelation:
Rev 22:19 and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book.
People definitely can have a “part” in the Book of Life, and then have that part revoked. That is the normal assumption about the Book of Life, throughout the Bible (the Book of Life is not unique to the Revelation context).
Piper’s theology does not allow for this, so he invents a mechanism in which the author of Revelation is making a claim that can never be actualized. John describes names being removed from the Book of Life, although such a thing could never occur (at least in Piper’s theology). This doesn’t fit the context of the quotes, which are warning people to stay true to God and to refrain from actions that will disqualify them from the Book of Life. Piper, wishing to have his cake and eat it too, admits as much:
Never, never, never be cavalier or trifling about your perseverance. God uses real warnings to keep us vigilant and to keep us persevering. We are safe. But we are not careless. That is the point.
But Piper’s conclusions run counter to his theology.