Max Nix is seven years old and lives in a town called Winkelburg with his huge family. Everybody in Winkelburg has a suit. Every body except Max.
One day, a gigantic box arrives in the mail for the Nix family. Inside the box is a... bright mustard-yellow suit! First Max's father tries it on because it looks about his size. But he is a banker. No banker wears a suit like that! It's too yellow and bright.
With a little bit of stitching from Mama Nix, Max's eldest brother, Paul, tries it on. He says that he'll wear this suit for skiing the next day, but he changes his mind because he thinks his friends will laugh at him as the suit is too yellow.
This goes on and on. Each brother has a reason to not want the suit. Mama Nix has to keep on snipping and cutting at the edges until Max gets the suit. Max is very happy. He has his own suit! He says he will wear the suit "today and tomorrow and the day after that."
Everywhere Max goes and everything Max does, the suit is perfect for it. If the suit gets wet, it dries up immediately. If hay gets stuck to it, it's OK because hay is yellow too. Not a single person in Winkelburg has ever seen such a suit. If Max slides on ice, the suit doesn't tear because the cloth is extra-tough. If rain falls on it, the water slides right off. If anything happens to the suit, it doesn't matter because the suit is conditioned for everything. Max has the perfect suit!
The It-Doesn't-Matter Suit, illustrated by Rotraut Susanne Berner, is vivid and interesting. Sylvia Plath describes each of the brothers' situations in detail. Emil, one of Max's brothers, for example, likes riding the toboggan. But none of the other tobogganers wears such a bright suit. Emil thinks he'll look like a big show-off if he wears it.