First of an unfinished series begun in 1987, and the 5th book has been recently released.
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They have a post apocalyptic setting, and depict a world struggling to come to terms with the destruction caused by global nuclear holocaust. The series' protagonist, Elspeth Gordie, is a young girl with mental powers condemned by the series' main antagonists, the governing bodies known as the Council, and the Herder Faction.
I always end up re-reading these books, because as the series progreses the path Elspeth walks gets increasingly convoluted, and you get all those complex themes.