The Crystal Doors series does not have a new book coming out soon. The latest book, Sky Realm (Book 3), was published in June 2008.
The first book in the Crystal Doors series, Crystal Doors, was published in June 2006.
The Crystal Doors series primarily falls into the Heroic Fantasy / Sword & Sorcery genre. This young adult series was written for ages 12-17, but can be enjoyed by adults too.