The Black Dragon by W. D. Newman
Approx. 83,400 words.
Published on August 5, 2012.
Ben, Casey, and their Grandma must join forces once again with Amos, the shape shifter, to save Camelot from the dragon that's bent on destroying it. But first, they must rescue their friends, Gabriel and Hob, from Kahzidar and recover the staff of Merlin!