I suppose this book could be seen as the end of a trilogy: the Baum/Denslow collaboration. The two broke onto the children's book scene in 1899 with Father Goose: His Book, became best-sellers the next year with The Wonderful Wizard of Oz (which would be the crown jewel for both men), and then ended their partnership in 1901 with Dot & Tot of Merryland. (I did not count The Songs of Father Goose as Baum's involvement was minimal. The lyrics were his, but they had not been written for this project.)
Why Baum and Denslow ended their partnership here has always been a matter of debate. Some say it was because Denslow felt cheated with his royalties for The Wizard of Oz musical, but as this was about a year later, I find it hard to believe.
The more reasonable idea that has been going around is that Baum and Denslow had become independent of each other. I think so, though I do think that the closing of the Geo. M. Hill Company (who had published these books) was a factor in this.
Another possible factor is that Baum was not happy that Denslow used his characters without his permission, although Denslow was in his rights, as the two men had copyrighted their works together. While we often cite Denslow's The Scarecrow and the Tin-Man comic page as an example, it must not be forgotten that Denslow did some Father Goose pages beforehand.
So, with seemingly bright careers for both Baum and Denslow, why did they separate? We will never know for certain. It seems neither was particularly incensed against the other, but they never worked together again, aside from The Wizard of Oz musical. (I believe I recall that they were not exactly "chummy" in their meetings on that project, but I'm not sure.) What we do know is that Denslow died of pneumonia in 1915, penniless and drunk. Baum died of a stroke in 1919, not exceedingly rich, but enough to secure a home for his widow for the rest of her life.
But enough of that. Dot & Tot of Merryland opens with a little girl, Evangeline Josephine Freeland (or "Dot," as she is usually called, though "Dot" is a noticeable shortened form of the name "Dorothy), going to stay on an estate called Roselawn for her health.
One thing anyone who has read a decent Baum biography should know is that Roselawn was the name of the home that Baum grew up in Syracuse, New York. His detailed description of Roselawn shows that he definitely had some affection for the home of his boyhood days.
I almost wonder if Dot's illness was a little bit of Baum (he was a rather ill child) added to the character. Once could easily read into this and think that Baum felt that his health laid in his childhood, but that might be going in too deep. Some might also read into it the illness of his infant niece Dorothy. That may also be too deep.
Playing one day, Dot meets Tot Thompson, the Gardener's son. The two become fast friends and playmates and Dot plans a picnic by the river bank. The next day, the two set out for the river and find a boat. Climbing in it to play, they get so caught up that they don't realize they're being taken far from the shore until it is too late.
This is a gentler form of what Baum often did in his Oz stories: nature giving way to a land of fantasy. In the Oz books, it happens by way of a cyclone, a storm at sea, an earthquake, or a whirlpool. Each time, the characters likely expect they will die, but they survive and find themselves in quite a different place than they expected.
So it is with Dot and Tot: they are swept into a tunnel and arrive in a stony valley. Here, they meet the first odd inhabitant of Merryland: the Watchdog, an old man with a long beard that covers his entire body. He tells them where they are and they are forbidden to enter Merryland. However, as Dot and Tot can't go back and can't stay, they've no choice but to go on, and the Watchdog, being powerless to stop them, lets them.
The first of the seven Valleys of Merryland is the Valley of the Clowns. It is here that the "real" clowns are trained until they're ready to go join a circus. (It is explained that false clowns are not so amusing.) Dot and Tot stay the night with Prince Flippityflop, who offers them odd foods to eat, like pickled shoelaces and fried goldfish, and suggests they eat sawdust to keep them from becoming damp inside.
One cannot read very deeply into this book, where Baum has secluded the stereotypical delights of children in Valleys. The clowns' logic, however, is pure Baum humor. "You certainly can't expect wisdom in a country of Clowns," Flippityflop says, which sums it up well.
The next valley, they find, is made entirely of candy, with many of the people being made of stick-candy and marshallows. (Later on, we find out about chocolate servants and licorice children.) Because they are made of candy, when someone "dies" (or gets broken into too many pieces to be mended), they are divided among their best friends and eaten.
This chapter was not exactly controversial, but when Books of Wonder reprinted the book in 1994, they removed the reference to the servants being made of chocolate, as well as a remark that they were untrustworthy. This was of course so one could not claim that it was humor at an ethnic group's expense. One can't call Baum a racist for this, as such jokes were made all the time in his day.
The next valley is full of babies that fall from the sky in blossoms, where they are cared for by storks before being taken into the world. Yes, this is where babies come from. We don't care what your biology lessons told you...
The next Valley is the home of the Queen. Dot and Tot are confronted by little wooden soldiers, who are another of Baum's classic lampooning of the military: they're there to look pretty but are otherwise useless. The Queen herself is a large wax doll who lives in a palace where the servants are dolls. The Queen decides to adopt Dot and Tot as her princess and prince. The people of the city around the palace are also dolls, but these are asleep except when the Queen decides to awaken them. This gives the Queen a dark edge: she is in complete control of her subjects. Should they prove unmanageable, as they do when Dot and Tot spend a day with them while the Queen speaks with the Watchdog, she can put them to sleep with a few waves of her fairy wand.
Dot asks the Queen her name a few times, but the Queen is interrupted before she can answer. This happens a few more times in the book.
The Queen accompanies Dot and Tot through the remaining valleys, the first being a paradise of cats who have nothing to do but lounge around and eat all day and screech at the moon at night. (It seems the Baum family had a cat they were fond of. In a card commemorating their anniversary that Baum wrote, he noted that one of the few times that Maud was in tears was when their cat had died.)
The next valley is run by Mr. Split: a man made of various types of wood who splits in two so he can wind up his mechanical animals twice as fast. This is Baum's interest in new technologies and old creating psuedo-life forms with them, a theme he would more famously re-visit in Tik-Tok the Clockwork Man, who debuted in Ozma of Oz. Baum also had another wooden man who was made to live up to his name in John Dough & The Cherub.
The final valley is very somber: it is filled of heaps of lost things: pins, needles, overshoes, toys, even wallets and money. Tot manages to find a doll he had lost, and the Queen lets him keep it, since it no longer belongs in a place for lost things, since he now knows where it is.
Here, the Queen makes her decision: Dot and Tot will never be fully happy in Merryland, and as this is against Merryland's most important law, she allows them to go home, by sending them through the exit tunnel from Merryland, which she closes after they pass through.
Dot and Tot arrive home at Roselawn, where they find both of their fathers looking for them. (Baum established in later works that he believed that no one should be looked down on because of their station, but seen as equals.) Later, Tot tells Dot he has deduced the Queen's name.
Like I said, this book is not one of Baum's deepest. Surely many bits were based on things Baum loved as a child and through his life. If you look into it too deeply, you lose the entertainment of the story, which is simply delightful and fun.
There are a few text-only editions of Dot and Tot of Merryland available. The only recent illustrated edition was the 1994 edition illustrated by Donald Abbott, instead of reprinting Denslow's illustrations. Abbott's illustrations were modeled on Denslow's style, but whatever charm Denslow had in his un-childish children, circus animals and clowns, Abbott failed to replicate. If you dig around, you can find a copy of this.