The Gnome King of Oz was Ruth Plumly Thompson's 1927 Oz title. I've never liked the fact that the character was now the Gnome King, rather than the Nome King - the change occurred in Kabumpo in Oz. Admittedly, it does correct what could be perceived as a spelling error, but the character was originally named the Nome King and I think he should remain that way. Chances are, it was a publishers' decision rather than Thompson's own preference.
This book introduces Peter from Philadelphia, one of Thompson's boy characters, who returns in later Oz books as well. L. Frank Baum tended to send girls to Oz, Thompson sent boys - I suppose she may have been trying to balance things out!