The Poirot books take readers through the whole of his life in England, from the first book (The Mysterious Affair at Styles), where he is a refugee staying at Styles, to the last Poirot book (Curtain[?]), where he visits Styles once again. In between, Poirot solves cases outside of England as well, including perhaps his most famous case, Murder on the Orient Express.
While the majority of the supporting cast in the Poirot stories is always different, some characters do show up more often. Arthur Hastings, whom Poirot met almost immediately after arriving in England, becomes his life-long partner and appears in many of the novels and stories. Other frequently recurring characters include the detective novelist Ariadne Oliver[?], who is clearly Agatha Christie's humorous self-caricature. Chief Inspector Japp of Scotland Yard appears in many of the stories, as well.
Movies Poirot has appeared in movies, too, played by Tony Randall[?] (The Alphabet Murders[?], 1965), Albert Finney (Murder on the Orient Express), and Peter Ustinov (Death on the Nile[?] and other films). However, many think the definitive Hercule Poirot portrayal is by David Suchet, who appeared in several television episodes made by Granada Television from the 1990s (which are often rerun on the A&E channel in the U.S.). The television dramatisations starring Suchet appeared under the series title Poirot.
See also Jane Marple.