What does Revelation 20:15 mean?

It is clear from this verse that only the presence of a person's name in the Lamb's book of life keeps them from being cast into the lake of fire. God keeps accurate records. All who have trusted in Jesus as Savior have their names written in the book of life (John 6:37; Philippians 4:3). Hebrews 12:23 refers to "the assembly of the firstborn who are enrolled in heaven." John 1:12 promises that whoever believes in the name of Jesus receives the right to become a child of God.

John 3:36 distinguishes between those who believe in the Son of God and those who do not obey Him. The former have eternal life; the latter languish under the wrath of God. In his first letter John assured his readers that "whoever has the Son has life; whoever does not have the Son of God does not have life" (1 John 5:12). The difference between spending eternity in heaven or spending it in the lake of fire comes down to the question: "Is the Son of God in my life or not?"

As this chapter closes, the victory over sin and evil is complete. Every single wrongdoing, crime, or hurt will have been punished. For those who accepted Christ's sacrifice on their behalf, His blood brings them forgiveness (John 3:16–18). For those who reject Him, their own sins result in eternal damnation (Romans 6:23).