Warning: Wikipedia contains spoilers
Major characters were based upon actual historical personages, including the character Blackthorne who was based on the english trader William Adams.
In the novel, the lead character is John Blackthorne, Pilot and acting Captain of the ship Erasmus which is one of the first of the foreign ships to reach the Japans. Despite an inhospitable welcome to the island, Blackthorne slowly gains an understanding of the people and their culture, and eventually learns to deeply respect it. The native Japanese people also grow to respect the strange 'barbarian' and he is eventually granted the unique status of Samurai.
The novel has been adapted as a movie, a television mini-series, and even an Infocom computer game.