Neither God nor prayer is mentioned at all in the book, at least not specifically. The book's very existence presented problems to Martin Luther (to name just one), at least for a while. He complained: "It hath too much of Judaism, and a great deal of heathenish naughtiness." [Luther's Works, Vol 3]. The book is written in a way unlike any other Bible text. There's a strong strain of patriotism and Jewish nationalism. It also has a distinct element of humor. That's not humorous levity, however. It's still Word of God and it deals with serious topics as it depicts events that occurred in Persia about 475 years before Christ. But since biblical times it has been regarded as canonical by the rabbis. And, according to Maimonides (Judaism's most famous scholar), second only to the Torah in importance.
Fact #2: Esther's husband was likely the same king who fought the Greeks at Marathon, from which we get the Marathon foot-race.
This would've been during the reign of Xerxes the Great, (a.k.a "Ahashuerus" in the KJV translation). Xerxes ruled an enormous empire of 127 provinces "from India to Ethiopia" as Esther 1:1 says. He was intent on humbling the Greeks, but was defeated on the plains of Marathon by a combined force of Greek city-states in 490 BC. According to legend, the messenger Pheidippides ran the approximate 25 miles to announce the defeat of the Persians to the Athenians. Then he dropped dead from exhaustion.
Fact #3: Either Xerxes or his father Darius is the same king that Nehemiah received permission from to rebuild the walls of Jerusalem during the Babylonian Captivity.
This was likely due to how impressed they were by the amazing acts of the Hebrew God that the Persians heard about during the events of the Babylonian Exile, even as far back as the humbling of Nebuchadnezzar and his conversion to faith in the God he thought his god had conquered. The Jews in Xerxes' time were slaves and exiles in Persia, "hold-overs" from their former slavery to the previous empire of Babylon, and its king, Nebuchadnezzar.
Fact #4: Though God is not mentioned in "Esther", it's evident that Esther's uncle Mordecai had faith in Him, and that Esther herself prayed to Him.
Why? Because of these two statements: the first by Mordecai, the second by Esther:
"For if you remain completely silent at this time, relief and deliverance will arise for the Jews from another place, but you and your father's house will perish. Yet who knows whether you have come to the kingdom for such a time as this?" [Esth. 4:14]
Here it's evident that Mordecai had complete faith that God would deliver the Jews from certain genocide, either with Esther's help, or without her help.
"Go, gather all the Jews who are present in Shushan, and fast for me; neither eat nor drink for three days, night or day. My maids and I will fast likewise. And so I will go to the king, which is against the law; and if I perish, I perish!" [Esth. 4:16]
Here it's evident that Esther and her maidens also prayed. The Bible prescribes fasting for two purposes, and they almost always go together: a) as a sign of deep grief and mourning, and b) as an aid to effective, importunate prayer: the kind of prayer reserved for extraordinary circumstances. When you are "importuning" God, when you are pleading with Him to intervene in a situation that's critical, you fast. The point? Both God and prayer are present in this book that mentions neither one specifically.
Fact #5: The Haman-Mordecai animosity began with a blood feud 500 years before either one was born!
The Book of Esther makes a point of emphasizing the forebears of both Haman and Mordecai. Mordecai was a descendant of King Saul's father Kish. [I Sam. 9:1] [Esth. 2:5]. Haman was a descendant of Agag, King of the Amalekites. [Esth. 3:1]. 500 years before in Israel, King Saul was told by God to exterminate the race of Amalek for their great wickedness. This he refused to do. So 500 years later, Haman attempted to do this very same thing with the Jews! The national moral to the story? Obey God in history, or "history" will take its revenge on YOU.".
Fact #6: Haman's death, which originally was planned for Mordecai, was by "hanging upon gallows" [Esth. 5:14, Esth. 7:10], but the execution wasn't by rope or strangulation. It was by impalement on a stake.
That's right, Gentle Reader. Not "Western" style, but "Vlad the Impailer" style. The Persians were cruel, and the Romans equally so. Neither people practiced the kind of execution we're familiar with in the West. Death by dropping from a platform or even being strung up with a rope noose and asphyxiated is quick and comparatively merciful. But the pagans of antiquity preferred their lowest criminals to die by slow torture. That's what Haman had in mind for Mordecai. Both Persians and Romans also used more merciful methods but impalement upon a stake was reserved for the worst criminals. When the Bible speaks of Christ "hung upon a tree", what's in view here is piercing and slow death on a cross-tee. If Haman had succeeded in executing Mordecai, and then all the Jews of the known world [Esth. 3:13-15], then he would've wiped out the family line of Jesus, and prevented the only "impalement" that could've saved humanity!