This description of the Book of Esther is from Easton's Bible Dictionary
Esther, Book of: The authorship of this book is unknown. It must have been obviously written after the death of Ahasuerus (the Xerxes of the Greeks), which took place B.C. 465. The minute and particular account also given of many historical details makes it probable that the writer was contemporary with Mordecai and Esther. Hence we may conclude that the book was written probably about B.C. 444-434, and that the author was one of the Jews of the dispersion.
This book is more purely historical than any other book of Scripture; and it has this remarkable peculiarity that the name of God does not occur in it from first to last in any form. It has, however, been well observed that "though the name of God be not in it, his finger is." The book wonderfully exhibits the providential government of God.
This description of Esther is from Easton's Bible Dictionary
Esther: the queen of Ahasuerus, and heroine of the book that bears her name. She was a Jewess named Hadas'sah (the myrtle), but when she entered the royal harem she received the name by which she henceforth became known (Esther 2:7). It is a Syro-Arabian modification of the Persian word satarah, which means a star. She was the daughter of Abihail, a Benjamite. Her family did not avail themselves of the permission granted by Cyrus to the exiles to return to Jerusalem; and she resided with her cousin Mordecai, who held some office in the household of the Persian king at "Shushan in the palace." Ahasuerus having divorced Vashti, chose Esther to be his wife. Soon after this he gave Haman the Agagite, his prime minister, power and authority to kill and extirpate all the Jews throughout the Persian Empire. By the interposition of Esther this terrible catastrophe was averted. Haman was hanged on the gallows he had intended for Mordecai (Esther 7:9-10); and the Jews established an annual feast, the feast of Purim (which see), in memory of their wonderful deliverance. This took place about fifty-two years after the Return, the year of the great battles of Plataea and Mycale (B.C. 479).
Esther appears in the Bible as a "woman of deep piety, faith, courage, patriotism, and caution, combined with resolution; a dutiful daughter to her adopted father, docile and obedient to his counsels, and anxious to share the king's favour with him for the good of the Jewish people. There must have been a singular grace and charm in her aspect and manners, since 'she obtained favour in the sight of all them that looked upon her' (Esther 2:15). That she was raised up as an instrument in the hand of God to avert the destruction of the Jewish people, and to afford them protection and forward their wealth and peace in their captivity, is also manifest from the Scripture account."