I have read this series and am in love with it. Truely amazing books.
Chronicles of Narnia-C.S.Lewis
A highly praised series of books. I never personally read all of them, but the ones I have read were great.
Enchantress of the Stars-Sylvia Engdahl
Another lesser-known author and another great book. Enchantress of the Stars is almost a mix between Science-Fiction and Fantasy, providing a wonderful novel.