God says the earth is his footstool (take that, earth) and heaven is his throne. Then, surprisingly, he asks who can build a house for him, implying that temples built by humans can't contain him.
He says, instead, that he'll look to people who are humble and contrite and who follow his word.
The sacrifices that people offer him—whether of oxen, sheep, grain, or frankincense—actually appall and disgust him (which may contradict things God says in other parts of Isaiah, depending on how you interpret them).
The people who worship in these offensive ways are going to get punished. ("Wait, but you told us to!") God will turn away from them.
And the people who pretend to be pious, but reject those who really do follow God, will also be put to shame. ("Okay, well that we expected.")
Next, Isaiah says that no one has ever heard of a woman giving birth without going through the pains of labor first. So why should Jerusalem giving birth to righteousness be any different?
But paradoxically, Isaiah says that Jerusalem gives birth to her children and skip that nasty labor thing. God asks, again rhetorically, whether he, the deliverer, won't follow through and deliver the child Jerusalem is giving birth to. (He will. Duh.)
God urges everyone to rejoice in Jerusalem and be nursed at her breast. God says that he too will comfort them like a mother comforting her child.
The good people will thrive like flourishing grass. But God also says that he's going to execute a furious judgment against the wicked with fire and with chariots like a whirlwind. Widespread panic (not the jam band, sorry) and death will ensue.
The people who hold illicit ceremonies in gardens and eat pork and vermin and other gross foods (Brussels sprouts, etc.) will all get wiped out.
God is going to send out emissaries from the survivors of this destruction all over the world.
They'll bring back people to worship God from every part of the globe, all arriving in Jerusalem, the same way that the Israelites already bring grain offerings in clean vessels. Some of them will even become priests.
The new heavens and the new earth will remain, and everyone will come on the Sabbath to worship God.
But they'll be able to look out on the dead bodies of the people who rebelled against him. (Nothing like a little site-seeing.) A worm that never dies and a fire that never burns out will continually eat and burn these corpses—a permanent reminder against any sort of rebellion.