I realized about 3/4 of the way through the book when a character mentioned how young the protagonist is, that it's really YA. But I hadn't noticed until then. It's great SF, just young protagonists. Her website says she started the first book when she was 14.
In this tiny area called the Land (the southern end of an island), there were areas spared from the GreatWhite (a nuclear world war). There's still dangerous "poisoned" places inland, but the coastal areas are clean. Over the years since the GreatWhite, two oppressive groups developed: The Council, wielding secular authority, and the Herders, wielding spiritual authority. They both believe in burning Seditioners (people who don't follow their rule) and Misfits (some are what we would consider retarded or with Down Syndrome, but most have elements of psi powers).
Our story starts with Elspeth, a 12-year-old whose parents were burned for Sedition, in an orphan home. She's been able to keep her Misfit status from everybody for a long time. When she is found out, she goes to court and someone from a work farm in a mountainous region buys her from the Council. After a day's journey (two changes of horses for the carriage), she arrives at a large compound where she is locked in a room. As she learns more about where she is and who she is, dangerous and thrilling events happen. This continues through both books, and each book sufficiently finishes the immediate problem, but there is a longterm quest forecast for Elspeth and I reckon that continues in the next books.
Highly recommended. Apparently most of her work, largely YA with lots of awards, was only published in Australia. I thnk I may spend some time finding other series and books.