An autobiography is a self-written chronicle of one's own life. By their very nature, autobiographical writings are subjective.
A formal book-length autobiography might range from the personal writings done during life that were not necessarily meant for publication (such as letters, diaries, journals, memoirs, and reminiscences).
There are four very general categories that an autobiography can fall under: thematic, religious, philosophical, and fictionalised.
The Americanization of Edward Bok (1920) and Mein Kampf by Adolf Hitler are among the novels in the first category (1925, 1927).
Augustine and Kempe, as well as the autobiographical chapters of Thomas Carlyle's Sartor Resartus and John Henry Cardinal Newman's Apologia from the 19th century, are just a few of the outstanding works that fall under the category of religious autobiography.
Several intellectual autobiographies were written in the late 19th and early 20th centuries, notably The Education of Henry Adams and the intensely analytical Autobiography of the philosopher John Stuart Mill.
Finally, an autobiography that has been subtly changed into a book might be thought of as being somewhat equivalent to the novel as a biography. The Way of All Flesh by Samuel Butler, A Portrait of the Artist as a Young Man by James Joyce, The Last Puritan by George Santayana, and the Thomas Wolfe novels are among the works in this category.
However, all of these works have components of all four genres; the best autobiographies frequently ignore these distinctions.

In some instances, inaccurate or misleading information has been provided as a result of the author's inability—or unwillingness—to accurately recollect memories. It has been highlighted by certain sociologists and psychologists that autobiography enables the author to reconstruct history.