The Bible is unified by profound themes running through it. Although it contains a number of major themes, here are three of the most important:
1. Jesus Christ
Not only does the New Testament give us the life and teachings of the Son of God, much of the Old Testament includes prophecies of His first and second comings (Luke 24:44 Luke 24:44And he said to them, These are the words which I spoke to you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.
American King James Version×). The greatest event of the past was Christ's first coming to earth as God made flesh. The greatest event in the future will be His second coming as glorified God in power and majesty. Although few understand this, Jesus Christ was the Creator and God in the Old Testament, acting on behalf of the Father (see John 1:1-14 John 1:1-14  In the beginning was the Word, and the Word was with God, and the Word was God.  The same was in the beginning with God.  All things were made by him; and without him was not any thing made that was made.  In him was life; and the life was the light of men.  And the light shines in darkness; and the darkness comprehended it not.  There was a man sent from God, whose name was John.  The same came for a witness, to bear witness of the Light, that all men through him might believe.  He was not that Light, but was sent to bear witness of that Light.  That was the true Light, which lights every man that comes into the world.  He was in the world, and the world was made by him, and the world knew him not.  He came to his own, and his own received him not.  But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:  Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.  And the Word was made flesh, and dwelled among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
American King James Version×; Hebrews 1:1-2 Hebrews 1:1-2  God, who at sundry times and in divers manners spoke in time past to the fathers by the prophets,  Has in these last days spoken to us by his Son, whom he has appointed heir of all things, by whom also he made the worlds;
American King James Version×; Colossians 1:13-16 Colossians 1:13-16  Who has delivered us from the power of darkness, and has translated us into the kingdom of his dear Son:  In whom we have redemption through his blood, even the forgiveness of sins:  Who is the image of the invisible God, the firstborn of every creature:  For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
American King James Version×; 1 Corinthians 10:4 1 Corinthians 10:4And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
American King James Version×). To fully understand, you will want to read the booklet Jesus Christ: The Real Story.
"God is love" (1 John 4:8 1 John 4:8He that loves not knows not God; for God is love.
American King James Version×, 16). The two "great commandments" are love for God and love for neighbor (Matthew 22:35-40 Matthew 22:35-40  Then one of them, which was a lawyer, asked him a question, tempting him, and saying,  Master, which is the great commandment in the law?  Jesus said to him, You shall love the Lord your God with all your heart, and with all your soul, and with all your mind.  This is the first and great commandment.  And the second is like to it, You shall love your neighbor as yourself.  On these two commandments hang all the law and the prophets.
American King James Version×). The Ten Commandments and God's other laws show us how to love God and how to love other people. The Bible is a love story—God's love for the whole world and how all people must learn to love God and others in turn (John 3:16 John 3:16For God so loved the world, that he gave his only begotten Son, that whoever believes in him should not perish, but have everlasting life.
American King James Version×; 1 John 3:16 1 John 3:16Hereby perceive we the love of God, because he laid down his life for us: and we ought to lay down our lives for the brothers.
American King James Version×; 5:3).
"Jesus" means "God Is Salvation," and He came to "save His people from their sins" (Matthew 1:21 Matthew 1:21And she shall bring forth a son, and you shall call his name JESUS: for he shall save his people from their sins.
American King James Version×). The greatest set of miracles related in the Old Testament was the deliverance of Israel out of Egyptian slavery. That and all the other times that God rescued His people are symbolic of the miraculous spiritual liberation, conversion and transformation of those whom God calls out of their spiritual Egypt "into the glorious liberty of the children of God" (Romans 8:21 Romans 8:21Because the creature itself also shall be delivered from the bondage of corruption into the glorious liberty of the children of God.
American King James Version×). This is only possible because of the supreme sacrifice Christ made for us so our sins can be forgiven and we can be saved by His grace (Ephesians 2:8 Ephesians 2:8For by grace are you saved through faith; and that not of yourselves: it is the gift of God:
American King James Version×).