The Invisible Fiends series does not have a new book coming out soon. The latest book, The Darkest Corners (Book 6), was published in June 2014.
The first book in the Invisible Fiends series, Mr Mumbles, was published in February 2010.
The Invisible Fiends series primarily falls into the General Fiction genre. This middle grade series was written for ages 8-12, but can be enjoyed by older readers as well.