Tradition holds that Jude is the “servant of Jesus” and the brother of James, the brother of Jesus. Like the second and third letters of John, Jude is one of the shortest books of the New Testament.
The text is uniquely rife with allusions to the controversial Book of Enoch, as well as alluding to a now lost book that detailed a story of the Archangel Michael and Satan arguing over the body of Moses (the Hebrew Testament of Moses).
Jude’s letter, like many of the other letters of the New Testament, was written to encourage the people of the early church to bind together, as in the “end days,” in order to be strong and graceful in perseverance against ungodly people.
The tone of the letter is harsh, not unlike certain Pauline letters, but it also (harshly) encourages love and unity, ironically.
As with some of the letters of the New Testament, Jude was written with the intention of being read aloud in one church, but also to be distributed widely. That is, the letter contains a particular as well as a universal message.