The Book of Malachi is about the prophecies that Malachi spoke to the Jews who had returned from Babylon to Judah. At that time, the Jews were discouraged even though they had finished building a new temple. The wonderful things that previous prophets had promised for Judah had not yet happened. And the Persian Empire still ruled over them. As a result, they no longer were concerned about the law or worshiping Yahweh. Malachi rebuked them for not trusting in Yahweh. But he also promised them that Yahweh would do everything that he promised to do.
This book traditionally has been titled "Malachi" or "The Book of Malachi." Translators may decide to call it "The Book about Malachi" or "The Sayings of Malachi." (See: [[rc://en/ta/man/translate/translate-names]])
The prophet Malachi wrote these messages from Yahweh to the Jews. However, since "Malachi" means "my messenger," it is possible that this was a title for this prophet. If so, we do not know his real name.
Malachi spoke about "the day" several times. This is the same as "the day of Yahweh." In the Book of Malachi, this is the time when Yahweh would judge his people. He would remove those who wickedly sin and bless those who trust in him. (See: [[rc://en/tw/dict/bible/kt/dayofthelord]] and [[rc://en/tw/dict/bible/kt/sin]])