Mikael Krogerus (Author) Mikael Krogerus is a Finnish journalist who works as an editor on Switzerland's biggest weekly magazine, Das Magazin. Roman Tsch¿eler (Author) Roman Tsch¿eler is a creative producer based in Biel, Switzerland, who produces documentary movies, ad campaigns and art installations. Krogerus and Tsch¿eler met at school in Denmark and have written four books together - The Question Book, The Test Book, The Change Book and the international bestseller, The Decision Book.