There are eight references in New Testament to the “book of life,” and two of them refer specifically to the book of life that belongs to the Lamb, Jesus Christ. Seven of the references appear in the book of Revelation. Those whose names are written in the book of life are those who belong to God, those who have attained eternal life.
Paul refers to those who have labored alongside him as those whose names are in the book of life (Philippians 4:3), again identifying the book of life as a record of the names of those who have eternal salvation. In the same way, Revelation 3:5 refers to the book of life in which the names of believers in the Lord are found. These are those who overcome the trials of earthly life, proving that their salvation is genuine. This verse also makes it clear that once a name is written in the book of life, Jesus promises that He will never blot it out, proving once more the doctrine of eternal security. The Lord Jesus, who is speaking to the churches in this part of Revelation, promises to acknowledge his own before His Father. Conversely, Revelation 20:15 reveals the fate of those whose names are not written in the book of life—eternity in the lake of fire.
Revelation 17:8 clarifies when the names of the redeemed are written in the book of life: “The inhabitants of the earth whose names have not been written in the book of life from the creation of the world will be astonished when they see the beast” (emphasis added). The names of those who approve of the Antichrist are not found in the book of life, and the names that are in the book of life were written there before the world was created. Thus, Revelation 17:8 teaches both eternal security and election.
In Revelation 13:8 and 21:27, we find the references to the "Lamb’s book of life," in which also are the names of all those who have been washed by the blood of the Lamb, Jesus Christ. The Lamb who has been “slain from the creation of the world” has a book in which are written all those who have been redeemed by His sacrifice. They are the ones who will enter the Holy City, the New Jerusalem (Revelation 21:10) and who will live forever in heaven with God. Since the book of life is that which records all who have eternal life through the Lamb, it’s clear that the book of life and the Lamb’s book of life are one and the same.