Cap'n Bill and Trot are the characters from the other author series. Their appearance here makes this installment a crossover. Crossover or not, the overall plot is very similar to that of the previous book. These two people were sucked in a giant whirlpool
and ended up in an unknown place. They had a lot of adventures and met some exotic creatures trying to get to civilization - the Land of Oz in this case.
If you think it sounds familiar - Dorothy was in this same situation at least 4 times before and so was Betsy Bobbin in the last book - you are absolutely right. Continuing with the similarity of the previous book, this one was named after another old favorite character who appeared well in the second half of the tale and did not have time to do anything exciting whatsoever. Last time it was Tik-Tok and this time it was Scarecrow's turn. Ozma and Dorothy make a guest appearance at the very end in both cases.
This installment was supposed to be Baum's favorite, but I did not find it such because of all the repetitions I mentioned above. It was entertaining enough to be better than 2 stars and annoying enough (read: riddled with plot-holes) to be worse than 4 stars, so 3 stars it is. At this point I will continue with the series for two reasons: the books are short and I want to read the last Baum's book - something about its reviews made me curious.