These two books are the sequels to Patrica Wrede’s The Thirteenth Child. Each is well written and largely self-contained. There’s continuity, but most of the threads wrap up at the end of each book.
These two books cover much shorter spans–not a whole childhood, only a year or two per book. In each, Eff grows, changes, and understands something new. She’s a great character, and it’s a pleasure watching her come to maturity. The west proves fascinating to explore alongside Eff and her friends.