The Bible contains several vague references to a heavenly book. This book can be considered the Book of Life. In this book, whether literal or figurative, are the names of all who are living (or, alternatively, all who are God’s people). This book also (or alternatively) contains the list of good or bad done by these people. Blotting people out of the book is used either for physical death or for disqualification as God’s people, perhaps coupled with future physical death.

The first possible reference to a Book of Life is found in Exodus 32. The situation is that the people have rebelled against God. Moses, on Mount Sinai, pleads for the people. God acquiesces Moses. Moses descends the mountain, rallies the Levites to kill the worst offenders, and then returns to speak to God. Moses pleads that God take out His wrath on Moses instead of the people:

Exo 32:32 Yet now, if You will forgive their sin—but if not, I pray, blot me out of Your book which You have written.”
Exo 32:33 And the LORD said to Moses, “Whoever has sinned against Me, I will blot him out of My book.
Exo 32:34 Now therefore, go, lead the people to the place of which I have spoken to you. Behold, My Angel shall go before you. Nevertheless, in the day when I visit for punishment, I will visit punishment upon them for their sin.”
Exo 32:35 So the LORD plagued the people because of what they did with the calf which Aaron made.

Moses states that God has a book, a book God has written (either literally or figuratively). The book is used to list those who are alive and/or righteous. Being blotted out is physical death or the equivalent to being added to God’s hit-list. Moses wants God to blot him out (presumably kill him). God states He “will blot [the unrighteous] out”. God states He “will visit punishment upon them for their sin” on a future day. The ideas seem to be linked, one and the same. Being “blotted out” doesn’t necessarily mean instant death, but “death” and being “blotted out” had some relation. God then plagues the people in order to hurt and kill those who have had their name blotted out.

In Psalms, David describes some sort of global list of living and/or righteous people.

Psa 69:26 For they persecute the ones You have struck, And talk of the grief of those You have wounded.
Psa 69:27 Add iniquity to their iniquity, And let them not come into Your righteousness.
Psa 69:28 Let them be blotted out of the book of the living, And not be written with the righteous.

David asks that his oppressors (equated with God’s enemies) are removed from the book “of the living”. The implication is that these people are possibly still in this book and that they would die (or be eventually killed) if removed. In this case, David is referring to some sort of book listing out people who are alive. David then reveals that the proper use of the book is for the righteous. In David’s worldview, the natural progression was from unrighteousness to death. In this sense, listing the names of the unrighteous alongside the names of the righteous was a overturning of the proper order of things.

In Psalm 87, one of the sons of Korah writes about God’s holy city:

Psa 87:6 The LORD will record, When He registers the peoples: “This one was born there.” Selah

This sentence is in the context of God especially liking Zion (Jerusalem). God’s love for Jerusalem even causes Him to value someone born in Jerusalem more than others. God is said to record this information in a book. In this book, there is a list of names accompanied by personal information including their place of birth. Does this book contain the names of all people? Just the righteous? We are not told.

In Isaiah, there seems to be a book used to list out the living:

Isa 4:2 In that day the Branch of the LORD shall be beautiful and glorious; And the fruit of the earth shall be excellent and appealing For those of Israel who have escaped.
Isa 4:3 And it shall come to pass that he who is left in Zion and remains in Jerusalem will be called holy—everyone who is recorded among the living in Jerusalem.

Isaiah describes a list of names of those still living. Again, this could be metaphorical. The idea is that after a great purging of Jerusalem then everyone remaining in the book will be righteous. Like David’s concept, the wicked are purged from the Book of Life.

In Daniel, a similar book serves to help judgment of both the living and the dead:

Dan 12:1 “At that time Michael shall stand up, The great prince who stands watch over the sons of your people; And there shall be a time of trouble, Such as never was since there was a nation, Even to that time. And at that time your people shall be delivered, Every one who is found written in the book.
Dan 12:2 And many of those who sleep in the dust of the earth shall awake, Some to everlasting life, Some to shame and everlasting contempt.

In Daniel, this book seems to contain information about a person’s life, both righteous people and unrighteous people. From this information, people are categorized into either eternal life or eternal death. God seems to be the one using the book to make judgment. The purpose of the book seems to be to inform God about how to act.

In Malachi, a similar book is said to have been written:

Mal 3:16 Then they that feared the LORD spake often one to another: and the LORD hearkened, and heard it, and a book of remembrance was written before him for them that feared the LORD, and that thought upon his name.
Mal 3:17 And they shall be mine, saith the LORD of hosts, in that day when I make up my jewels; and I will spare them, as a man spareth his own son that serveth him.
Mal 3:18 Then shall ye return, and discern between the righteous and the wicked, between him that serveth God and him that serveth him not.

In Malachi, there seems to be a concern among those who worship God that God will not remember who is righteous and who is unrighteous. The righteous talk among themselves, and God listens. God seems to mitigate their fears by writing a spiritual(?) book which lists out those who fear God. This book, like other mentioned books, lists out righteous individuals and might contain deeds that they have done.

Paul uses the Book of Life as some sort of global list of those who are God’s people:

Php 4:3 And I urge you also, true companion, help these women who labored with me in the gospel, with Clement also, and the rest of my fellow workers, whose names are in the Book of Life.

To Paul, being in the book was equated to being a true Christian. Perhaps Paul is using this book in a new sense or echoing the use in Exodus.

The Book of Life might be metaphorical or it may be a heavenly book. It may be a cultural idiom, used with flexibility to refer to life and death, to righteous and damned. The understanding of the book is that people are written into the book along with things about those people. The book records the living and lists the righteous. Being stricken from the book is synonymous with rejection by God, current rejection with possible future physical death.