Metamorphosis

The Metamorphosis is the most famous of Kafka's works, along with The Trial and The Castle. 

The story begins when a salesman, Gregor Samsa, wakes up to find himself transformed into a giant insect and becomes an object of disgrace to his family, an outsider in his own home, a quintessentially alienated man. A harrowing meditation on human feelings of inadequecy, guilt, and isolation, "The Metamorphosis" has taken its place as one of the most widely read and influential works of twentieth-century fiction.