The Book of Life is the book God and Jesus Christ have that records the names of those who are saved. Those whose names are not written in the Book of Life are cast into the Lake of Fire. This Book is used at the Great White Throne judgment in Kingdom Come.

It is not known whether the Book of Life is updated throughout history, or written at the beginning of it and never modified afterwards. Ephesians 1:4-5 says that God had chosen some to be blameless before Him before the foundation of the world. The Left Behind series subscribes to "once saved, always saved", at least during the dispensation of the Tribulation and Millennial Kingdom, since those who become saved are unable to choose the Mark of Carpathia when challenged to take it. There are no recorded attempts for the unsaved to argue about its contents; instead, all those who are unsaved, including great philosophers and legislators, limit themselves to lamenting their fate and passively going into the Lake of Fire.

In The Mark, Tsion Ben-Judah says in one of his Internet newsletters that in a subsequent letter he would explain the difference of the Book of Life and the Lamb's Book of Life. Cameron Williams had never heard of such a difference before, but he eagerly anticipated learning more about the distinction. The "Book of Life" and "the Lamb's Book of Life" are mentioned once each in the next book, Desecration, both by Tsion Ben-Judah, in another newsletter, but due to the death of a "beloved colleague", Tsion Ben-Judah did not elaborate.

In other religious groups

Islam has a similar notion of the "preserved tablet" al-Lawhu 'l-Mahfuz that contains the determination of God regarding every event, including the state of salvation of individuals. Some Muslims believe that there is a literal tablet but others see it as a metaphor for the qadar of Allah. Qadar literally means "power" but the term often has connotations of predestination.