"Karlsson-on-the-Roof" is a children's book series written by Swedish author Astrid Lindgren. The stories revolve around a mischievous and charming character named Karlsson, who lives on the roof of a house in Stockholm. He has the ability to fly and often gets into various adventures with a young boy named Svante. The series is known for its humor and imaginative storytelling. The first book, published in 1955, introduces readers to Karlsson's playful personality and his friendship with Svante. The stories highlight themes of friendship, imagination, and the joy of childhood. Karlsson-on-the-Roof has been translated into multiple languages and remains popular among children worldwide.