Welcome to Jude!
Below is helpful information I found in Fee and Stuarts Book, “How to Read the Bible Book by Book:“
Orienting Data for Jude
Content: a pastoral letter of exhortation, full of strong warning against some false teachers who have “secretly slipped in” among them
Author: Jude, who modestly describes himself as “the brother of James” (thus of Jesus), but does not consider himself an apostle (v. 17)
Recipients: unknown; probably a single congregation of predominantly Jewish Christians somewhere in Palestine who were well acquainted with both the Old Testament and Jewish apocalyptic literature
Occasion: the threat posed by some itinerants who have turned grace into license and who have “wormed their way in” (NEB) to the church
Emphases: the certain judgment on those who live carelessly and teach others to do so; the importance of holy living; God’s love for and preservation of his faithful ones
Overview of Jude
Jude begins and ends on the note of God’s call and preservation of his people (vv. 1–2; 24–25). The body of the letter is in two parts: Verses 3–19 warn against the false teachers; verses 20–23offer exhortations to perseverance and advice on how to help those who have been influenced by the false teachers.
The warning against the false teachers is sandwiched between descriptions of their ungodly behavior (vv. 3–4, 17–19). The meat of the sandwich (vv. 5–16) is a midrash (a kind of Jewish commentary) on some Old Testament and Jewish apocalyptic passages similar to 2 Peter 2, which offer precedents both as to the lifestyle of and God’s sure judgment on the false teachers.
Specific Advice for Reading Jude
You can hardly miss the fact that the false teachers are the crucial matter. Fortunately, enough is said about them that we can piece together a picture of sorts. They have been accepted within the community as Christians (v. 4) and participate in their love feasts (v. 12). Very likely they are itinerant “prophets” (well known to us from other early Christian sources like the Didache), described as dreamers (v. 8) who in fact “follow mere natural instincts and do not have the Spirit” (v. 19).
Their teaching appears to be some form of libertinism: They have perverted “the grace of our God into a license for immorality” (v. 4) and follow their own evil desires (vv. 16, 18) like “unreasoning animals” (v. 10). That they “pollute their own bodies” in the “very same way” as Sodom and Gomorrah (“sexual immorality and perversion,” vv. 8, 7) probably points to at least one dimension of their license. They also “reject authority and heap abuse on celestial beings” (v. 8, the latter is an indication of a Jewish Christian milieu with its reverence for angels), being “grumblers and faultfinders” (v. 16) who would divide the community (v. 19).
The fact that such people are destined by biblical decree to come under God’s judgment and Jude’s obvious concern for those who have been influenced by them (v. 23) indicate the seriousness of the problem.