Tik-Tok of Oz marks the end of what I'd call the lavish Oz books - after this title, the books fell into a regular pattern with no new surprises like stamped covers, metallic inks or color throughout. This was the last Oz book to have a cover plate from a finished John R. Neill watercolor, and the last to have color endpapers. Apparently, Reilly & Britton had intended this title to have another wrap-around dustjacket, as the artwork for that survives, but this was dropped in favor of repeating the cover plate - I'd assume it was a less expensive alternative.
This book has the famous color endpapers featuring a map of Oz in front, and a map of the lands surrounding Oz in the back. Many inconsistencies have been found with these maps, not least of which are the reversal of east and west on the compass points. This has lead to a lot of discussion as to what Baum may have intended with his various fantasies.
I've always been intrigued by the 3rd state of Tik-Tok from 1918 - in this volume, the endpaper maps are printed in green rather than full color. That's the last time they are used in the book. I've never quite understood why the maps were dropped - once color endpapers were no longer in use, they could easily have been printed in black & white.
Much of the artwork for this book survives - in fact, I think Patchwork Girl and Tik-Tok are the two Baum books with the most Neill artwork around.