The premise of the strip is very simple. The Princess of Slumberland (she's never named, she is just 'the Princess') wants a playmate, and Nemo is the playmate she wants. Emissaries from the Land of Dreams are sent to bring him to the royal palace before he awakes. McCay is a master at playing out every conceivable variation on an idea. Keeping in mind that this was a weekly strip, it took about five months to get him to the palace and then another five months to actually get him in to meet his Princess.
The reason it takes to long is simple: at the end of each page, Nemo wakes up! Often it's because, in the unpredictable world of dreams, things can take a frightening turn and scare the boy. In one case he is taken to Slumberland through a cave of glass, where the Glass People live. He is so taken with their princess that he can't resist kissing her. She breaks. Soon everyone breaks and the whole community is reduced to shards! Upset at what he's done, he awakes. (As an aside, people often remark on the influence McCay had on Sendak, but the Glass Guards remind me a lot of the Kashira in Miyazaki's Spirited Away.) Once they get to the castle, Nemo is often awakened by a competitor for the Princess' attention, Flip. Flip is first described as the son of the Sun, but he is later demoted to being the nephew of the Dawn Guard. Either way, he has connections and can cause the sun to rise whenever he wants; waking Nemo and destroying Slumberland. Until the next night, anyway.
The effort the court is willing to go to keep Flip away begins to bother Nemo and his sympathy is awakened. Soon it':s agreed that the best way to deal with him is to at least pretend to include him in their adventures. One such adventure takes them to the Candy Islands, where the Jungle Imps live. One of them joins the cast and the core characters - Nemo, Flip and the Imp - are united. They have several adventures in Slumberland, and a few in Nemo's own world, where they are joined by the Kid. Later they are captured by apes and put on display at the Monkey-land Zoo: Early Ancestors Of Our Race, Captured In The Wilds Of Unclesamland. And that's where second volume started. Or will start, for you with the sense to start at the beginning!
It's interesting to see the development of Nemo and of McCay's approach to storytelling. At the start he captioned each panel, often retelling what we can plainly read for ourselves. Then he used the title panels to give a summation of the strip, at first even describing its conclusion! Finally, by the time Nemo finally meets the Princess, McCay trusts the medium and his readers enough to just tell the story. All of these strips when printed when Nemo was being published by the Herald. In the second volume editor Cammie Ledbetter remarked that the strip's later publishing history affected the strip, and reading these earlier ones and seeing how much more smoothly it all flows, I can better understand the effect changing publishers had.
This volume actually starts with Tales of the Jungle Imps, a strip that preceded Nemo and introduced the Imp. In it the Jungle Imps are a group of mischievous, well, imps who go around torturing and otherwise harassing animals for sport. How the animals respond to this accounts for how the turtle got its shell, why the hyenas laugh, etc. This is a particularly weak strip for McCay. The racism of the caricatures is obvious, but the verse is what really drags it down. McCay doesn't show any skill for writing verse at all.* Kipling's Just So Stories were published just the year before the Imps and McCay':s work is too obviously a poor copy (though it is interesting to realize that these men were contemporaries).
As I have said before, McCay is a pioneer that all comic lovers should be familiar with, and this volume gives readers the man at the height of his powers. His innovative and beautiful line work - his use of perspective and skewed perspective, his panels, his cityscapes, his grasp of the nature of dreams - make this a volume you should add to your collection.
* NOTE: McCay was the artist for Jungle Imps, but not the writer. See Cammie Ledbetter's comment below. My mistake.