This series is now a modern classic for all fantasy lovers aged 9+, and is a wonderful next read if you love Philip Pullman, Mortal Engines or Star Wars.
These books begin with a rebellious character: Kestrel Hath. Living in the walled city state of Aramanth, she is tired of all its rules. She soon enough learns the secret of the wind singer with her twin brother, Bowman. And together they will set out on a terrifying journey to the true source of evil that grips their home.
If you're looking for an epic story that with spectacular stakes and highs, this is one of the best magical and fantasy series for readers aged 9 and 10.
All the Wind on Fire books in order:
Book 1: The Wind on Fire (2000)
Book 2: Slaves of the Mastery (2001)
Book 3: Firesong (2002)