Oz books series that were not written by L. Frank Baum

Below is a list 19 titles that Ruth Plumly Thompson wrote from Oz books series, with a copyright year and publisher of the 1st editions

15. The Royal Book of Oz (1921, Reilly & Lee)
16. Kabumpo in Oz (1922, Reilly & Lee)
17. The Cowardly Lion of Oz (1923, Reilly & Lee)
18. Grampa in Oz (1924, Reilly & Lee)
19. The Lost King of Oz (1925, Reilly & Lee)
20. The Hungry Tiger of Oz (1926, Reilly & Lee)
21. The Gnome King of Oz (1927, Reilly & Lee)
22. The Giant Horse of Oz (1928, Reilly & Lee)
23. Jack Pumpkinhead of Oz (1929, Reilly & Lee)
24. The Yellow Knight of Oz (1930, Reilly & Lee)
25. Pirates in Oz (1931, Reilly & Lee)
26. The Purple Prince of Oz (1932, Reilly & Lee)
27. Ojo in Oz (1933, Reilly & Lee) view 12 color plates
28. Speedy in Oz (1934, Reilly & Lee)
29. The Wishing Horse of Oz (1935, Reilly & Lee)
30. Captain Salt in Oz (1936, Reilly & Lee)
31. Handy Mandy in Oz (1937, Reilly & Lee)
32. The Silver Princess in Oz (1938, Reilly & Lee)
33. Ozoplaning with the Wizard of Oz (1939, Reilly & Lee)

John R. Neill, famous illustrator of Oz books, wrote these three titles:

34. The Wonder City of Oz (John R. Neill, 1940, Reilly & Lee)
35. The Scalawagons of Oz (John R. Neill, 1941, Reilly & Lee)
36. Lucky Bucky in Oz (John R. Neill, 1942, Reilly & Lee)

You can find the remaining four first edition collectible Oz titles below

37. The Magical Mimics in Oz (Jack Snow, 1946, Reilly & Lee)
38. The Shaggy Man of Oz (Jack Snow, 1949, Reilly & Lee)
39.The Hidden Valley of Oz (Rachel R.Cosgrove, 1951, Reilly&Lee)
40. Merry Go Round in Oz (Eloise Jarvis McGraw and Lauren McGraw Wagner, 1963, Reilly & Lee)