"What is he doing inside?" is a science fiction novel by American writer Fritz Leiber that challenges readers to think about the nature of human-machine interaction. In this work, Leiber brings to great reflection what is hidden behind the laboratory door. The main character - the wife of a scientist - tries to understand what is happening behind the shadowy walls when her husband spends many hours in his work. This book captivates the reader from the first page and leaves many mysteries unknown until the last. Fritz Leiber's fluidity of speech and ability to build tension make What's He Doing Inside? an exciting sci-fi journey beyond reality.