Harvey’s Hideout by Russell Hoban, illustrated by Lillian Hoban, 1969.
Summer is difficult for the Muskrat kids this year. Their friends are away for the summer, and Harvey and his older sister Mildred are getting on each other’s nerves. But, there’s nothing that says they have to spend the whole summer with each other.
Harvey builds himself a raft and tells Mildred that he’s going off to meet with members of his secret club for a cookout where annoying big sisters aren’t welcome. Mildred says that’s fine with her because she’s been invited to a party where there will be no annoying little brothers. Harvey says that’s fine with him . . . except that it really isn’t.
The secret hideout where Harvey has been spending his time is empty except for him and the comic books he brought with him, and his cookout is for only one person. He just made up the story about the secret club to make Mildred jealous and to have an excuse to spend time away from the house and her. Harvey appreciates the freedom, but he’s also bored and lonely and envies Mildred, wondering who she knows who is still in town, inviting her to parties every day.
Then, when Harvey tries to make some improvements to his secret hideout, he discovers that he’s not the only one to dig a secret hideout for himself in the area.
This is a nice story about sibling rivalry and cooperation. One of the parts I like best is early on in the story when Harvey and Mildred’s father lectures them for fighting and insulting each other (I hated it when I was a kid, but I kind of like it now because I realize what the father is actually trying to say). He points out that there is some truth in their insults, but they’re wrong about each other at the same time. Part of the reason they fight is because they each have their faults (Harvey can be selfish and Mildred can be bossy), but they each unfairly assume that the other is a lost cause and that they can never be friends. It’s only when they come to realize that they’re equally lonely (Mildred has been having tea parties with just her doll) and Harvey makes the first move in offering to share what he has with Mildred that they realize that they can each be the friends they both need this summer.
When I was a kid, I wished I had a hideout like theirs! I also love the colorful illustrations in the story.
The book is currently available online through Internet Archive.