Apparently, Peter has spent his time between Acts 4 and now going from an illiterate speaker of Aramaic to a fluent writer of Greek. Or, you know, this letter is a fake.
'Peter' writes to the elect (v. 2), who will know who they are based on whether god sprinkled some of Christ's blood on them. If so, you're going to heaven when the world ends. Don't look like Carrie? Sorry, you're SOL. Meantime, be sober and judge people for their works.
Be nice and control your lusts and Peter will use you as a stone in his building of worship. Also, brag about your good works to people and obey the king, who will punish evildoers. Slaves ought to fear their masters.
We haven't talked about women for awhile, so let's do that now. Women have to obey, of course, but at the same time, their obedience has to win non-christian husbands over. It doesn't seem to occur to anyone that a wife converting while her husband remains a pagan is pretty disobedient. She also can't beguile him into faith through sexy tricks like hair braiding, lingerie or fancy jewellery. She has to be dowdy like the old testament matriarchs.
Husbands have to honour their wives as the weaker vessel (v. 7), be compassionate to others, and not get caught up in vengeance cycles. Plus, bad people can't harm you if you're faithful. Of course, if you do suffer, it's god's will, just like when Jesus died and went to hell to talk to the sinners. Furthermore, christians should be prepared to discuss their faith with anyone who asks.
'Peter' also explains to us where baptism comes from: apparently, when everybody except for Noah's family died in that flood way back when, it was actually god saving people, and dunking your head now will also get you saved. No, it is not explained what the connection between saving people by keeping them dry and saving them by getting their hair wet might be.
Suffering means you aren't sinning. This will also allow you to finally give up thinking sexy thoughts like those whoring pagans and think about god until the world ends.
'Peter' also wants to tell us that Jesus went down to hell once to give the sinners a chance to repent.
Be good, be charitable, and for heaven's sake, don't murder anyone, no not even when the apocalypse starts. Speaking of apocalypses, it will be much worse for non-believers.
'Peter' reminds the elders to take care of their flocks and the younger members to obey their elders. All people should remember that the devil,
as a roaring lion, walketh about, seeking whom he may devour (v. 8).