Engaging The Dragon question

I often struggle with character development and wonder if the book could be improved by more careful editing, perhaps with a view to fully fleshing out some of the principal characters? I thought of making a sequel or prequel to Engaging the Dragon, and this could be an opportunity for further character development. My WIP, soon to be released, is an off shoot of Engaging the Dragon, starring Timothie Hill and the Cloak of Power, set on Earth, but with three Draxxt characters. I'm hoping to rectify the original's mistakes in this newest book.