What the rest of the Bible says
The book of life and the lake of fire
Revelation describes the dead, great and small, standing before a great white throne, and anyone not found written in the book of life being cast into the lake of fire, the second death.
What John saw
Revelation is full of symbols, and Christians interpret its details in different ways. Its message here is plain: there is a final judgment, and being written in the book of life is what matters.
11I saw a great white throne and him who sat on it, from whose face the earth and the sky fled away. There was found no place for them. 12I saw the dead, the great and the small, standing before the throne, and they opened books. Another book was opened, which is the book of life. The dead were judged out of the things which were written in the books, according to their works. 13The sea gave up the dead who were in it. Death and Hades gave up the dead who were in them. They were judged, each one according to his works. 14Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire. 15If anyone was not found written in the book of life, he was cast into the lake of fire.
Revelation 20:11-15 (WEB) · context
How a name is written there
Revelation calls it the Lamb's book of life. The Lamb is Jesus, who gave His life for sinners.
27There will in no way enter into it anything profane, or one who causes an abomination or a lie, but only those who are written in the Lamb’s book of life.
Revelation 21:27 (WEB) · context
29The next day, he saw Jesus coming to him, and said, “Behold, the Lamb of God, who takes away the sin of the world!
John 1:29 (WEB) · context
The good news
Jesus came to save you from this
God loves you and gave His Son so that whoever believes in Him should not perish.