Road To Oz by Baum L. Frank
'Are you going to Ozma's party?'Princess Ozma's birthday celebration is set to be the most magnificent party of all time and everybody who's anybody in Oz is desperate for an invitation. As for Dorothy and her friends lost out in the lands beyond the Deadly Desert they mustuse their heads and discover a way to get back to the Emerald City if they are to be in attendance. But will they manage to get there on time?