I really enjoyed
Parable of the Sower and the trilogy
Lilith's Brood (its original title was Xenogenesis), both by Octavia E. Butler, but I can't find digital versions.
Parable of the Sower takes place in the immediate future, in a California whose economy is devastated by global warming (water is so expensive that being dirty becomes fashionable).
Lilith's Brood takes place after a nuclear war; a mysterious race of aliens help the few survivors to rebuild their lives... but according to those aliens' rules.