In this fourth installment Dorothy and her cousin Zeb fall through an earthquake to the center of the earth (it's fantasy people!) They meet up with the Wizard from the first book. Solid addition to the series.
The Emerald City of Oz suffers from the same issue as The Road to Oz... too many characters, too little plot. I did prefer this one to RtO though as it seemed better spaced, and there actually was some plot with the Gnome invasion. I also liked Aunt Em and Uncle Henry's reaction to Oz, even if they ...