The Merlin Spiral series does not have a new book coming out soon. The latest book, Merlin's Nightmare (Book 3), was published in May 2014.
The first book in The Merlin Spiral series, Merlin's Blade, was published in April 2013.
The Merlin Spiral series primarily falls into the Heroic Fantasy / Sword & Sorcery genre. This middle grade series was written for ages 8-12, but can be enjoyed by older readers as well.