Because he's insane, Isaiah exalts god for destroying Jerusalem. Yet somehow he has protected the poor and given them refuge from storms and heat. You know what really protects from water and sun? A house.
Next, god cordially invites you to a mountain-top feast for all the people of the world. As a grand finale, he'll rid the world of death. And people will praise him. Well, people will praise anyone who cooks for them, especially if they don't then have to do the dishes.
All the world's people, that is, save for the Moabites. They're going to be thrown on the dungheap like old straw.
A song about holy cities and only the righteous being allowed inside. There will be perfect peace because no one will live there. He will also punish bad people. He calls on righteous people to obey god's laws and tells us how eagerly he's awaiting god's return.
Isaiah admits that the Israelites have strayed in their exclusive relationship with god and promises that NOW he's the only one for them. They thank him for killing off their enemies and increasing their territory and disciplining them when they needed it. He then makes ANOTHER reference to women in childbirth like, dude, get a new simile. Then we're told that dead people will come back to life and the living will rejoice rather than run away in terror. He encourages those self-same living to go home and hide out until god's in a better mood, because he's coming around now with punishing on the brain.