For emphasis purposes I have enlarged the text where "Book" (in various forms) is mentioned in biblical texts... also in some places I have inserted my comments in brackets () which may be of help in scripture interpretations.
Biblical references...
Exodus 20:3... You shall have no other gods before Me.
Exodus 32:31-34... So Moses returned to the Lord and said, “Alas, this people has sinned a great sin. They have made for themselves gods of gold.  But now, if you will forgive their sin—but if not, please blot me out of your book that you have written.”  But the Lord said to Moses, “Whoever has sinned against me, I will blot out of my book. 
Psalm 56:8... You have kept count of my tossings; put my tears in your bottle.  Are they not in your book?
Psalm 69:28... Let them be blotted out of the book of the living; let them not be enrolled among the righteous.
Psalm 103:3... (God) who forgives all your iniquity...
Psalm 103:12... as far as the east is from the west, so far does he (God) remove our transgressions from us.
Psalm 139:16... Your eyes saw my unformed substance; in your book were written, every one of them, the days that were formed for me, when as yet there was none of them.
Isaiah 43:25... “ I (God) am he who blots out your transgressions for my own sake, and I will not remember your sins.
Daniel 12:1... At that time shall arise Michael, the great prince who has charge of your people.  And there shall be a time of trouble, such as never has been since there was a nation till that time.  But at that time your people shall be delivered, everyone whose name shall be found written in the book.
Malachi 3:16... Then those who feared the Lord spoke with one another. The Lord paid attention and heard them, and a book of remembrance was written before him of those who feared the LORD and esteemed his name.
Matthew 12:36-37... I tell you, on the day of judgment people will give account for every careless word they speak, for by your words you will be justified, and by your words you will be condemned.”
Luke 10:17-20... The seventy-two returned with joy, saying, “Lord, even the demons are subject to us in your name!” And he said to them, “I saw Satan fall like lightning from heaven.  Behold, I have given you authority to tread on serpents and scorpions, and over all the power of the enemy, and nothing shall hurt you.  Nevertheless, do not rejoice in this, that the spirits are subject to you, but rejoice that your names are written in heaven.”
John 3:16-18...  “For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.  For God did not send the Son into the world to judge the world, but that the world might be saved through Him.  He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God.
John 12:47-48... If anyone hears my words and does not keep them, I do not judge him; for I did not come to judge the world but to save the world.  The one who rejects me and does not receive my words has a judge; the word that I have spoken will judge him on the last day.
John 14:21... Whoever has my commandments and keeps them, he it is who loves me.  And he who loves me will be loved by my Father, and I will love him and manifest myself to him.”
Acts 3:19... Repent therefore, and turn back, that your sins may be blotted out..
Romans 8:29... For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers.
Ephesians 1:4-5... even as he chose us in him before the foundation of the world, that we should be holy and blameless before him. In love he predestined us for adoption to himself as sons through Jesus Christ, according to the purpose of his will.
Ephesians 1:13... In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit...
Ephesians 3-6... Blessed be the God and Father of our Lord Jesus Christ, who has blessed us in Christ with every spiritual blessing in the heavenly places, even as he chose us in him before the foundation of the world, that we should be holy and blameless before him.  In love he predestined us for adoption to himself as sons through Jesus Christ, according to the purpose of his will, to the praise of his glorious grace, with which he has blessed us in the Beloved.
Hebrews 12:23... and to the assembly of the firstborn who are enrolled in heaven, and to God, the judge of all, and to the spirits of the righteous made perfect,
1st Peter 1:1-2... Peter, an apostle of Jesus Christ.  To those who are elect exiles of the Dispersion in Pontus, Galatia, Cappadocia, Asia, and Bithynia, according to the foreknowledge of God the Father, in the sanctification of the Spirit, for obedience to Jesus Christ and for sprinkling with his blood: May grace and peace be multiplied to you.
1st John 5:11-13... And this is the testimony, that God gave us eternal life, and this life is in his Son.  Whoever has the Son has life; whoever does not have the Son of God does not have life.  I write these things to you who believe in the name of the Son of God, that you may know that you have eternal life.
Philippians 4:3... Yes, I ask you also, true companion, help these women, who have labored side by side with me in the gospel together with Clement and the rest of my fellow workers, whose names are in the book of life.
Revelation 3:5... The one who conquers will be clothed thus in white garments, and I will never blot his name out of the book of life. 
Revelation 7:4... And I heard the number of the sealed, 144,000, sealed from every tribe of the sons of Israel:
Revelation 13:8... and all who dwell on earth will worship it, everyone whose name has not been written before the foundation of the world in the book of life of the Lamb who was slain.
Revelation 17:8... The beast that you saw was, and is not, and is about to rise from the bottomless pit and go to destruction. And the dwellers on earth whose names have not been written in the book of life from the foundation of the world will marvel to see the beast, because it was and is not and is to come.
Revelation 20:11-15... Then I saw a great white throne and him who was seated on it. From his presence earth and sky fled away, and no place was found for them.  And I saw the dead, great and small, standing before the throne, and books were opened. Then another book was opened, which is the book of life. And the dead were judged by what was written in the books, according to what they had done.  And the sea gave up the dead who were in it, Death and Hades gave up the dead who were in them, and they were judged, each one of them, according to what they had done.  Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire.  And if anyone’s name was not found written in the book of life, he was thrown into the lake of fire.
Revelation 21:27...  But nothing unclean will ever enter it, nor anyone who does what is detestable or false, but only those who are written in the Lamb’s book of life.
Revelation 22:19... and if anyone takes away from the words of the book of this prophecy, God will take away his share in the tree of life (King James version of the bible translates the term as book of life) and in the holy city, which are described in this book.

Discussion Thoughts:
Listed above are 15 mentions of the "book of life" (or versions) that are documented in our current bible.  Our current bible does not include several books (believed to be as many as 54) that are not included because they were eliminated from the bible when the final decision was made as to what books were to be included.  15 of the "54" books are published as the Apocrypha when the Protestant Church of the 1800's decided to remove those books from the bible as we know it today.  Some of those "other" books such as Enoch (not part of the Apocrypha) also mention the "book of life".

Question #1... when did the "book of life" originate?  The bible provides answers to that question... all the way back to Exodus 32:31-34 the "book of life" is mentioned.  Revelation 13:8 suggests that the "book of life" was written before the foundation of the world!  Revelation 17:8 suggests the same thing!  This seems to suggest that our names were written in the "book of life" before the foundation of the world!  Some say this is predestination... but that is NOT what the scriptures say!  Yes, our names were written before the foundation of the world... but the scriptures do not say our eternal salvation or death in the lake of fire was predetermined!!!  So, my conclusion is that our names do exist in God's book(s) and I do believe what the bible says... that my name was written in the "book of life" before the foundation of the world!  Knowing that our names were written in "book of life" before the foundation of the world creates some interesting thought processes... God knew what we were going to name our children even before we named them!!!

Question #2... what is written in the "book of life"?  Psalm 56:8... You have kept count of my tossings; put my tears in your bottle.  Are they not in your book? (a very clear statement that everything that transpires is written in the book).  Psalm 139:16... Your eyes saw my unformed substance; in your book were written, every one of them, the days that were formed for me, when as yet there was none of them. (again, some will say that this is predestination... I disagree!!!  Psalms was clearly saying that the "book" writes about "the days that were formed for David... IT DOES NOT SAY THAT DAVID HAD NO SAY IN THE FORMATION OF THOSE DAYS!!!... I believe he did!).  Malachi 3:16... Then those who feared the Lord spoke with one another.  The Lord paid attention and heard them, and a book of remembrance was written before him of those who feared the LORD and esteemed his name.  (This book is a bit different... a "book of remembrance" that lists those who feared the Lord, esteemed his name, and spoke with others who feared the lord... kinda sounds like a Church, doesn't it).  To conclude "what is written"... every deed we do, every word we speak, EVERYTHING THAT OCCURS IN OUR ENTIRE LIFE IS WRITTEN IN THE BOOK!!!

Question #3... how is the "book of life" used? Matthew 12:36-37... I tell you, on the day of judgment people will give account for every careless word they speak, for by your words you will be justified, and by your words you will be condemned.  (This does not specify that our words are written in a book... but God has a record of our every word... and as the scripture says... we will be justified or condemned by the words we have spoken).  Revelation 20:12... And I saw the dead, great and small, standing before the throne, and books were opened.  Then another book was opened, which is the "book of life".   And the dead were judged by what was written in the books, according to what they had done.  (These scriptures "say it all"... we will be judged by what is written in the books.  Again... a word to those who believe in predestination... these verses very clearly say that our eternal life is not predestined... our eternal life will be determined by what is written in the books).

Question #4... Can my name be blotted out of the "book"?  Exodus 32:31-34 says it very clearly... “But the Lord said to Moses, “Whoever has sinned against me, I will blot out of my book".  Exodus 20:3... You shall have no other gods before Me... (this seems to be one of the ways to be blotted out of His book)!  (Psalms 69 is interesting... a Psalms of David asking that God blot out those in the "book" who have trangressed against him... but the Psalms does not have an answer!). 

Question #5... Can my sins be blotted out of the "book"?  Isaiah 43:25... “ I (God) am he who blots out your transgressions for my own sake, and I will not remember your sins.  Acts 3:19... Repent therefore, and turn back, that your sins may be blotted out.  Revelation 3:5... The one who conquers will be clothed thus in white garments, and I will never blot his name out of the book of life. (So... yes our sins can be blotted out of the "book").

My Beliefs... This was an interesting and somewhat difficult study... my suggestion is to study the scriptures recorded above as well as other verses surrounding the scriptures to get a better idea of the overall context of the scriptures.  My conclusions of each of the 5 questions are written at the end of each question.
Final conclusions are simple... there is a "book" or "books" of life by which we will be judged in the "final" judgment... if we believe and subscribe to the scriptures of John 3:16-18 our name is written in the "book"!  Further... we all make mistakes along the way and those mistakes are written in the "book" (see Question #5... a few scriptures about our transgressions being blotted out).