A biography must cover the accounts of a person's life in the third-person. The biography can cover the subject's entire life or a distinct portion.
The accounts for a person's biography are based on another's perception of that person, which is different than an autobiography, which is a personal account of the writer's life.
According to The Telegraph, the best-selling biographies of all time include "Lives of the Twelve Caesars" by Suetonius, who served as a private secretary to all the Caesars; "The Life of Samuel Johnson" by James Boswell, which provides insight into an entire era and "The Life of Charlotte Bronte" by Elizabeth Gaskell, which offers an inside look at the great author's life.
