God is the unifying "character" of the Bible. From Genesis to Revelation, God is at the beginning and end of the story. Only Esther in its original form does not mention God.  Yet both Jews and Christians understand God to be behind its story, directing its course and vindicating His people. In the light of both canons, reading Esther as Scripture will presuppose God even though He is not mentioned.
The vast majority of the OT is henotheistic rather than properly monotheist. Henotheism is the belief that while many gods may exist, only one God is appropriate for worship. This God is not only the supreme God, but the God of Israel.
The NRSV captures the likely original of Deuteronomy 32:8-9 well:
"When the Most High apportioned the nations, when he divided humankind, he fixed the boundaries of the peoples according to the number of the gods; the LORD's own portion was his people, Jacob his allotted share."
Here we have a picture of the highest God, El Elyon, whose proper name is Yahweh (LORD) apportioning gods to the nations. He assigns Molech to Moab; He assigns Dagon to the Philistines, and so forth. But then He, the highest God, assigns Himself to Israel. Here we have the acknowledgement that there are other gods, but the LORD is the highest God and the one that Israel is exclusively to worship.
This picture, however literally we are to take it, also seems to stand behind Psalm 82:
"God has taken his place in the divine council; in the midst of the gods he holds judgment: 'How low will you judge unjustly...'
"I say, 'You are gods, children of the Most High, all of you; nevertheless, you shall die like mortals...'" (NRSV).
And of course this perspective might also explain the curious wording of a number of passages: "You will have no other gods before Me" (Exod. 20:3) and "Let us create humanity in our image" (Gen. 1:26). The vast majority of the OT would fall into this category. When we see Elijah contending with Baal or Hosea decries sacrifices to Asherah, the prophets seem to contend with real evil forces.
It is really with so called "second Isaiah" (40-55) that we encounter language of "pure" monotheism for the first time in the OT:
"I am the LORD, and there is no other; besides me there is no god" (45:5).
"Assemble yourselves and come together, draw near, you [Israelite] survivors of the nations! They [the nations] have no knowledge--those who carry about their wooden idols, and keep on praying to a god that cannot save" (45:20).
"To whom then will you liken God, or what likeness compare with him? An idol? -- a workman casts it, and a goldsmith overlays it with gold..." (40:18-19).
Christians and Jews of course would no longer want to use the word "god" in reference to the evil powers mentioned in the OT. Judaism itself at the time of Christ seems to have gone several ways in its conceptualization of these powers. The one path is that of the book of Wisdom, which like Isaiah 40-55 denies any reality behind idols:
"A skilled woodcutter may saw down a tree easy to handle and skillfully strip off its bark, and then with pleasing workmanship make a useful vessel that serves life's needs... But a cast-off piece from among them, useful for nothing, a stick crooked and full of knots ... he forms it in the likeness of a human being, or makes it like some worthless animal ... (13:11-14)
"[he] sets it in the wall, and fastens it there with iron. He takes thought for it, so that it may not fall, because he knows that it cannot help itself... (13:15-16)
"he asks strength of a thing whose hands have no strength" (13:19).
Paul apparently takes another Jewish trajectory, one that perhaps stands in greater continuity with the OT. In 1 Corinthians 10:20 he suggests that the one who sacrifices at a pagan temple is sacrificing to demons.
It is thus legitimately Christian to reconceptualize the gods of the OT as demonic forces subservient to God. Christians and Jews affirm that there is only one God.
The NT does not question the unity of God. Thus 1 Cor. 8:6 gives a sort of early Christian "creed" when it states that "for us there is one God, the Father, from whom are all things for whom we exist, and one Lord, Jesus Christ, through whom are all things and through whom we exist" (NRSV). Likewise, Ephesians 4:6 affirms that there is "one God and Father of all, who is above all and through all and in all." Even Jesus himself in Mark 10:18 alludes to the oneness of God when he responds to a young man, "Why do you call me good? No one is good but one, God."
These passages lead us to one of the central questions of NT Christology. The oneness of God is not in question in the NT. But these classical texts of God's oneness seem to affirm it in distinction from Christ. So there is one God in 1 Corinthians 8:6, yes. But Christ is distinguished from Him in a different category, "Lord." There is "one God and Father of all" in Ephesians 4:6, but distinguished from Him in the previous verse is the "one Lord" of 4:5. In this regard 1 Timothy 2:5 is striking, "there is one God, also one mediator between God and mortals, the man Christ Jesus."
Of course these verses only represent one side of the coin. We also have passages like Hebrews 1:8, where Jesus is addressed, "Your throne, O God, is forever and ever." Similarly, Titus 2:13 speaks of how believers await the appearance of "our great God and Savior Jesus Christ." And while it is a matter of significant debate, one way to punctuate Romans 9:5 would render it, "Theirs [the Israelites] are the fathers and from them is the Messiah according to the flesh, [who is] God blessed forever, Amen." 
The Gospel of John of course is replete with statements of the oneness of God and Jesus as Son. We will discuss John's use of logos imagery in the next section, but we might at least note his comment that "the logos was God" in 1:1. When Jesus says that "before Abraham was, I am" (John 8:58), he seems to equate himself with Yahweh at the burning bush.
Indeed, there are a number of places in Paul's writings where Paul relates the title "Lord" to Jesus by way of a passage that is strikingly monotheistic in the OT. When Paul, perhaps drawing on an early Christian hymn, tells of God giving Jesus "the name above all names" and then alludes to Isaiah 45:23, what name can he have in mind but Yahweh?  Romans 10:13 also relates Joel 2:32 to Christ as Lord. Both Isaiah 45:23 and Joel 2:32 are passages that strongly affirm that God alone is to be worshipped. To apply them to Christ is radical, for it implies that he is also worthy of worship, like God.
Larry Hurtado and others have drawn attention to the worship of Jesus in the NT implied in passages such as these.  For Hurtado, this worship of Jesus is in itself sufficient to speak of Christianity already having parted company from orthodox Judaism. He speaks of the "binitarian" form of early Christian worship.
The book of Revelation of course is striking in the way that the Lamb is worshipped alongside God. A standard feature of Jewish apocalyptic literature is that when an angel appears to a seer, that person falls down on his face. But then, there is almost always a "denial formula," where the angel tells the seer to get up because only God is worthy of worship. Amazingly, Jesus does not tell John to get up in Revelation. He receives John's worship!
This worship of Jesus alongside God has led Richard Bauckham to speak of God including Jesus within His unique identity.  Perhaps a better way to express this phenomenon is to say that to worship Jesus is to worship God. The NT seems for the most part to subsume the godness of Jesus within the godness of God the Father.
Thus, when we return to Hebrews 1:8-9, we notice that while Jesus is addressed as God, the author is using the language that Psalm 45:7 had earlier applied to the human king on his wedding day. Hebrews 1:9 goes on to draw a distinction between Jesus as God and Jesus' God: "therefore God, your God, has anointed you [as king]." Applying divine language to Jesus thus relates to his cosmic kingship. As in the OT, language of the king being God's Son is applied to Jesus in a significantly expanded way.
The NT draws extensively on Psalm 110:1 to speak of Christ's exaltation to God's right hand as cosmic king. We notice here again that there are two Lords in play: "the LORD said to my Lord, sit at my right hand..." Paul's use of Lord in reference to Christ sometimes seems to draw on both of these Lords! As we mentioned above, sometimes he clearly relates LORD passages in the OT to Jesus as Lord.
In the sections that follow, we will explore the relationships of Jesus and the Spirit to the Father within in the oneness of God. But it should be fairly clear from our discussion here that our Christian beliefs on these matters owe a great deal to the unfolding of God's revelation in the church in the centuries following the NT. It is perfectly appropriate for us as Christians to read the Scriptures with these beliefs fully intact. But the original meanings of the biblical texts themselves are far from clear on the relationship between the unity of God and the divinity of Christ.
 Deuterocanonical Esther, the Greek form found in the Roman Catholic and Orthodox OT, has remedied this problem with prayers to God.
 While the Dead Sea Scrolls have largely confirmed the text of the OT as it has survived in the medieval Masoretic Text, there are a few places where they have clarified places where the Greek OT, the Septuagint, varied from the existing Hebrew manuscripts. Deuteronomy 32:8 is one of those places where the DSS have confirmed that the LXX is more original than the MT.
 On balance, this rendering would be quite ununsual for Paul, as Titus is.
 One God, One Lord