There are those who want to say that the book of Esther is neither inspired nor beneficial but is simply a beautiful legend. They base their claim on the absence of God’s name.
While it doesn't appear directly in the text, there are evidently four instances of the Tetragrammaton, the Hebrew spelling of God's name, appearing in the form of an acrostic. At Esther 1:20; 5:4, 13; and 7:7 we find four successive words starting with the Hebrew letters for YHWH (or JHVH, from which we get the English form Jehovah [JeHoVaH]). These initials are made especially prominent in at least three ancient Hebrew manuscripts and are also marked in the Masora by red letters. At Esther 7:5, there is also an acrostic for EHYH, meaning 'I shall prove to be', which is tied in to the divine name as its definition (see Exodus 3:14-15).
Should the Book of Esther be a Part of the Hebrew Bible?
Many facts establish the record as authentic and factual. It was accepted by the Jewish people, who called the book simply the Meghil‧lah′, meaning “roll; scroll.” It appears to have been included in the Hebrew canon by Ezra, who would certainly have rejected a fable. To this day, the Jews keep the feast of Purim, or Lots, in celebration of the great deliverance in Esther’s time. The book presents Persian manners and customs in a lifelike way and in harmony with the known facts of history and archaeological discoveries. For example, the book of Esther accurately describes the way Persians honored a man. (6:8) And archaeological excavations have revealed that the descriptions of the king’s palace as given in the book of Esther are exact to the smallest detail.
All the evidence points to the book of Esther as being part of the Holy Bible, "inspired of God and beneficial." (2 Tim. 3:16) Even without directly mentioning God or his name, it provides us sterling examples of faith.
More about Esther:
Mordecai and Esther (My Book of Bible Stories; Watchtower Online Library)