Heavenly record (Luke 10:20; Heb 12:23) written by God before the foundation of the world (Rev 13:8; 17:8) containing the names of those who are destined because of God’s grace and their faithfulness to participate in God’s heavenly kingdom. Those whose names are in the book have been born into God’s family through Jesus Christ (Heb 12:23; Rev 13:8), remain faithful in worship of God (Rev 13:8; 17:8), are untouched by the practice of abomination and falsehood (Rev 21:27), are faithful through tribulation (Rev 3:5), and are fellow workers in the work of Jesus Christ (Phil 4:3). The book of life will be used along with the books of judgment at the final judgment to separate the righteous and the wicked for their respective eternal destines (Rev 20:12, 15: 21:27).
Christ Himself determines whether the names that are recorded in the book of life remain in that record and are supported by His confession that they belong to Him at the day of Judgment or are blotted out (Rev 3:5).
The OT refers to a record kept by God of those who are a part of His people (Exod 32:32; Isa 4:3; Dan 12:1; Mal 3:16). As in Revelation, God can blot out the names of those in the book (Exod 32:32; Psa 69:28). In the OT this may simply mean people not in the book die, leaving the list of the living. Those whose names are written in the book are destined for life in a restored Jerusalem (Isa 4:3) and deliverance through future judgment (Dan 12:1).