The Lost Key of Oz is an Oz novel that was intended to be a sequel to the Oz books of L. Frank Baum, Ruth Plumly Thompson, and John R. Neill. 

THE LOST KEY OF OZ
by Leslie Isabelle Frank

Written in 1999 in celebration of the Oz centennial, the author explains:

"When asked how the name 'Oz' originated, Wizard of Oz author L. Frank Baum often related the story that he happened to glance up and see a filecabinet drawer labeled 'O-Z' and decided to use that for the name of his magical land.  I never quite believed that this explanation was neccesarily the complete truth—it occurred to me that Mr. Baum, when creating his Wizard, may have been loosely inspired by Shelley's Ozymandias, but perhaps didn't want to lay claim to anything that could be seen as a literary pretension.  The Lost Key of Oz is my attempt to expand on this theory within the confines of the Oz universe."

Read the Lost Key of Oz