I'm not sure why I enjoy a good post-apocalyptic story so much, but I do have a taste for them, with the excellence of Michaela Roessner's
Vanishing Point being a high bar (though, strictly speaking, it's not exactly post-apocalyptic).*
And I adore H.M. Hoover. Her books were probably the first sci-fi I read, and they are still solid despite almost forty years' advances in technology. They're not all gems, but the balance is heavy on the side of quality.
Children of Morrow is definitely post-apocalyptic, and a terrific story of outcast kids escaping from hostiles to a better community. Tia and Rabbit are vivid characters and the world is described well--it's desperately lonely, and bleak enough to make one want to go out and mend the ecology on the spot.
Unfortunately, the sequel
Treasures of Morrow doesn't deliver quite as well. It synopsizes too much, skimming over the complexities of Morrow with just a few glimpses, and breaks down in characterization when the kids return to their original home. It's not a bad book, but it suffers in comparison with the well-rounded Children.
Still, I can recommend them both. Read the first, and enjoy; if you like it enough, read the second.
* I am aware of the deep flaws of her Walkabout Woman. Vanishing Point is much better, and to my possibly ignorant eyes avoids such errors.