The "book of life" refers to the heavenly record of all those people over the centuries who have trusted Christ as their Savior, and have followed Him as Lord. Some day, the Bible says, its pages will be opened, and all those whose names are found there will have the right to enter heaven.
If you've given your life to Christ, your name is already written there. Furthermore, Jesus has promised that if you belong to Him, nothing will ever be able to remove your name from its pages. He declared, "I will never blot out his name from the book of life, but will acknowledge his name before my Father and his angels" (Revelation 3:5). This promise should be written on the heart of every believer!
But what about those who have not turned to Christ in repentance and faith, and have rejected Him as their Lord and Savior? Their names are not written there -- and as a result, they have no hope of heaven. The Bible solemnly warns, "If anyone's name was not found written in the book of life, he was thrown into the lake of fire" (Revelation 20:15).
But listen: God loves you, and Jesus Christ came to save you and give you the gift of eternal life! Don't turn your back on Jesus Christ, but by a simple prayer of faith ask Him to come into your life and save you -- and He will.