The Kingdom on Fire series does not have a new book coming out soon. The latest book, A Sorrow Fierce and Falling (Book 3), was published in October 2018.
The first book in the Kingdom on Fire series, A Shadow Bright and Burning, was published in September 2016.
The Kingdom on Fire series primarily falls into the Fantasy genre. This young adult series was written for ages 12-17, but can be enjoyed by adults too.