Question:
What is the Book of Life? How do people get blotted out of the Book of Life? Revelation 22:19; Psalm 69:28.

Answer:
The actual phrase “book of life” is not found in the Scriptural references you give. In Revelation 22:19 it should read “tree of life.” This is the rendering in Mr. John Nelson Darby’s New Translation, and in other critical translations. Psalm 69:28 reads, “Let them be blotted out of the BOOK OF THE LIVING” and I believe it is referring to “those living on the earth at that time.” The context of this Psalm is dealing with the enemies of God and how they deserve to be judged by God. Verse 28 is simply stating that they deserve the death penalty; that is, to be removed from the land of the living. See also Psalm 109:13 where we see the same truth being presented.

There are several New Testament references though that speak of the “book of life” or the “Lamb’s book of life” (see Philippians 4:3; Revelation 3:5; 13:8; 17:8; 20:12, 15; 21:27). I have no doubt that in these verses (with the possible exception of Revelation 3:5) the book of life is referring to all who have eternal life (not just physical life, which Psalm 69:28 speaks of) through faith in the Lord Jesus Christ. It is referred to as “the book of the slain Lamb” (Revelation 13:8, JND version) and “the Lamb’s book of life” (Revelation 21:27) because only those who have been redeemed by the blood of the Lamb are recorded there. And all who have been redeemed have been given eternal life (see 1 Peter 1:18, 19, 23).
I stated that Revelation 3:5 may be an exception to this. The verse reads, “He that overcometh, the same shall be clothed in white raiment; and I WILL NOT BLOT HIS NAME OUT OF THE BOOK OF LIFE, but I will confess his name before My Father, and before His angels.” There are two possible interpretations:
(1) The book of life here is a record of Christian PROFESSION, not a record of REALITY. Mr. Walter Scott states, “It is profession which may or may not be real. The end would show. Some names would stand, others be erased.” Those who hold this view believe the context substantiates this interpretation, for the Lord said to those in Sardis, “Thou hast a name that thou livest, and art dead,” meaning that many professed to have life in Christ (and thus were written in the book of life), but were actually spiritually dead.(2) Others believe that this verse is no exception. One writes, “The reference, I think, is to the same book, and conveys the assurance of what the Lord will not do. The Lord’s Word declares the impossibility of being once saved then lost, or blotted out of the book of life.” He also says, “Why think we are dealing here with a different book (one of profession instead of reality) when there appears no intimation of it being different from all the other references?” (From 400 Questions and Answers.)