In Jewish tradition, the book of Malachi marks the end of divine prophecy. There is, however, no formal pronouncement of “that’s all folks,” since, y’know, Porky Pig is not kosher.
Malachi means “my messenger” or “my angel,” a name that echoes God’s vow in chapter 3, verse 1: “See, I am sending my messenger to prepare the way before me, and the Lord whom you seek will suddenly come to his temple. The messenger of the covenant in whom you delight—indeed, he is coming, says the LORD of hosts.” (NRSV) Predicting your own arrival is kind of a cheat when it comes to establishing your prophetic street cred, but hey, whatever works. Some scholars don’t believe that Malachi was a proper name, but just meant “my messenger,” so that the authorship is anonymous. (Source)
Malachi’s message is that God will judge Israel for its faithlessness but restore it in the end because he keeps his promises of the covenant in spite of everything.