I guess Baum wanted to write books outside of Oz, but he was cursed by the franchise's success. By 1914, a new Oz release must have been like a new Harry Potter book. After several forwards of Baum swearing that Oz is dead and buried, in books 8 through 10 we see him come to grips with his Oz-centric fate by trying some new takes on his formula.
Tik-Tok of Oz (1914)
Meet Betsy Bobbin, who is totally just Dorothy again, except that Baum doesn't feel like writing her this time. There's a bit of self-plagiarizing at work, as Betsy arrives in Oz via shipwreck (as Dorothy did, once upon a time) and Betsy comes across plant people who must be picked when they are ripe (as Dorothy did, once upon a time.) And just as Betsy equals Dorothy, her companion Hank the Mule is more or less a Jim the Cab Horse clone.
This book also insists on calling the Shaggy Man simply "Shaggy," as if that is his given name.
The big event in this one is wicked old Ruggedo getting kicked out of the Nome club, and his maligned major domo Kaliko inherits the throne. As far as Ozian fan service is concerned, this volume marks the revelation that Toto can talk, and has been able to since the moment he set foot in Oz. His first printed words are "All right, here I go!"
The Scarecrow of Oz (1915)
Meet Trot, who is totally Dorothy again. Trot comes to Oz via a sea cave, and, in the Baum tradition, has a grandfatherly old companion... a sailor named Cap'n Bill. One of Baum's things is to take his young leads and pair them up with creepy elderly people. In fact, as I'm reading this hundred-year-old books, it strikes me that there are a lot of passages that would be awfully funny if scanned in and taken out of context. Most of these situations revolve around the word "queer."
Now that we have these two books with non-Dorothy Dorothy girls, we start to see a new focus on Ozma as the ultimate dictatorial deus ex machina. She has banned all magic in Oz (except when practiced by her or her trusted lieutenants Glinda and the Wizard... although in later books we'll see Polychrome perform magic). Ozma can see anything she wants by spying with her Magic Picture. Glinda is informed of everything that happens in Oz via her Book of Records. Baum goes on at length about how everybody loves Ozma and everybody loves their job and everybody loves her chosen favorites. It starts to get really dangerous-sounding. You can see the seeds that Gregory Maguire seized on for his Wicked series.
It would not be a stretch to claim that Baum foresaw both television and the internet in his description of Ozma and Glinda's magical artifacts. The picture above shows Ozma, Betsy and Dorothy watching the Magic Picture and deciding at what point they will interfere with Trot's drama.
Anyway, "Scarecrow" ends up in one of Oz's overlooked corners (Jinxland) where nobody gives a crap about Ozma and her rules, which makes for more interesting story-telling. Oz-as-Utopia is pretty boring, basically one giant comfortable tea party for Ozma's monarchy. Naturally, Ozma (and Dorothy and Betsy) are revealed to be watching Trot's adventure, and they swing in at the very end to rescue Trot and company and shut down the rebellious Jinxlanders.
Rinkitink in Oz (1916)
This is a weird, not the least reason being that almost none of the book takes place in Oz. So the title is a misnomer. I would not be surprised to hear that Baum had this plot sketched out as one of his non-Oz books, but low sales figures encouraged him to paste some Oz into it.
"Rinkitink" takes place mostly on some islands several countries separated from Oz proper. In fact, we get a new, zoomed-out map to locate the island of Pingaree and its surroundings. Interestingly, while the new map includes Oz, it shows the now-familiar Oz countries reversed west to east. Screwy.
This book is actually quite a weighty adventure, and Clark really liked it even though most of his Oz favorites were nowhere to be seen. The lead this time is a young boy, Prince Inga, although he is saddled with another weird old man as his partner, King Rinkitink. Inga suffers some high drama right out of the gate, as a brutish race demolishes his home and kidnaps everyone on the island, including Inga's parents. This situation is easier for Clark to grasp than the usual Oz style of Child X wandering aimlessly and ending up living in the Emerald City. Inga also gets superpowers of a sort in the form of three hidden magic pearls, and Clark dug that secret power angle.
The Nomes return in "Rinkitink." Although chronologically the king is now Kaliko, he acts like an ass just as Ruggedo did.
The Lost Princess of Oz (1917)
After three books of mostly new characters, Baum returns to form in this book. We're back in Oz, now aflame with the population of the entire series to date. Baum, obviously aware that he wrote Betsy and Trot identically to Dorothy in their solo adventures, now invents simple personality traits to help us tell them apart. Betsy is suddenly the shy one, and Trot will be referred to as "Tiny Trot."
Very intriguing story this time... particularly if you enjoy, as I do, investigating the totalitarian nature of Ozma's regime. Everybody in Oz wakes up one morning to find Ozma missing, along with all of the famous magical instruments. The Magic Picture, the Book of Records, the Wizard's bag, etc. Ozma's entire power base is gone.
So just about everybody gets involved in the hunt for Ozma. The Patchwork Girl, the Woozy, Button-Bright (who keeps getting older and smarter, although he still wanders off and gets lost), etc. Even the Cowardly Lion returns, despite Baum's habit of regularly sidelining the Lion as he does with most of his Animal characters. In short, "Lost Princess" is a mega team-up. In comics terms, this would be the Summer Event.
We also get some new additions: Cayke the Cookie Cook, the Frogman, and the Lavender Bear (plus his fortune-telling robotic Pink Bear.) The villain this time out is Ugu the Shoemaker, who gets slapped down into hard reform at the end.
Only three books left in Baum's original run! We're actually on book #13 at the moment. I'll tease my upcoming coverage of book #12 by saying that it contains perhaps the single weirdest event in the entire published history of Oz.