One striking thing about The Wonderful Wizard of Oz, if you're mostly familiar with the adaptations, is how little of the novel is spent in Kansas. The famous film version spends a good amount of time, before whisking Dorothy away to Oz, establishing her home and the people she's going to be homesick for while she's away. So does the animated TV version that was my main touchstone for Oz when I was a boy. Baum, on the other hand, is all about the strange adventures in distant places, and we've barely arrived in Kansas and had a chance to look around before it's time to be off.
That said, Baum does make good use of the time, and efficiently gives evocative descriptions of the land and its inhabitants. (The word "gray" comes up a lot; one can see why the film opens the way it does.)