Wikipedia provides the definition of a novel as:
A novel is a long narrative, normally in prose, which describes fictional characters and events, usually in the form of a sequential story.
and that of an autobiography as:
An autobiography (from the Greek, αὐτός-autos self + βίος-bios life + γράφειν-graphein to write) is a written account of the life of a person written by that person.
I wonder if there is a word for books that describe, not the entire life but, a single incident from the author's life? For example, the one I recently read, Lone Survivor by Marcus Luttrell. Calling it a "story book" sounds extremely childish.