Question: "What is the Book of Life?"
Answer: Revelation 20:15 declares, “If anyone's name was not found written in the book of life, he was thrown into the lake of fire.” The Book of Life is the set of names of those who will live with God forever in heaven. It is the roll of those who are saved. This Book of Life is also mentioned in Revelation 3:5; 20:12; and Philippians 4:3. The same book is also called the Lamb’s Book of Life because it contains the names of those who have been redeemed by the blood of the Lord Jesus (Revelation 13:8; 21:27).
How do you get your name written in the Book of Life? Simply by repenting of sin and believing in the Lord Jesus Christ as your Savior from sin (Philippians 4:3; Revelation 3:5). The moment you place your faith in Jesus as your Savior (John 3:16; Romans 10:9‑10), your name is written in the Book of Life, never to be erased (Revelation 3:5; Romans 8:37‑39). No true believer should doubt his eternal security in Christ (John 10:28-30).
The Great White Throne Judgment described in Revelation 20:11‑15 is a judgment for unbelievers. That passage makes it clear that no one at that judgment has his name in the Book of Life (Revelation 20:12‑14). Since their names are not in the Book of Life, their fate is sealed, their punishment is sure.
Some people point to Revelation 3:5 as “proof” that a person can lose his salvation. However, the promise of Revelation 3:5 is clearly that the Lord will not erase a name: “He who overcomes . . . I will not blot out his name from the Book of Life.” An overcomer is one who is victorious over the temptations, trials, and evils of this world—in other words, one who is redeemed. The saved are written in God’s registry and have the promise of eternal security.
Another passage over which confusion sometimes arises is Psalm 69:28: “Let them [David’s enemies] be blotted out of the book of the living.” This “book of the living” should not be confused with the Lamb’s Book of Life. David is referring to earthly, physical life, not eternal life in heaven. The same is true of the “book” mentioned in Exodus 32:32-33.
God keeps good records. He knows His own, and He has set the names of His children permanently in His book.