As a result of the book's popularity, the term "Treasure Island" has passed into the language as a common phrase, and is often used as a title for games, amusement arcades, places, etc. (See Treasure Island (disambiguation).)
Warning: wikipedia contains spoilers
The "sea cook" of the title is Long John Silver, a villainous but charming sailor who ingratiates himself with the Hawkins family after the discovery of a map left behind at the inn managed by the mother of Jim Hawkins. Jim himself is the narrator. Some of the most respectable local citizens, including Squire Trelawney and Dr Livesey, are intrigued by the map, and set off to find the island, with Jim as cabin boy and Long John Silver as the leader of the crew. Once on the island, Silver betrays his employers, but his plans to desert them are foiled and the treasure is found.