The Three Musketeers - Alexandre Dumas
The Three Musketeers is a novel by Alexandre Dumas, first serialized in March–July 1844. Set in the 17th century, it recounts the adventures of a young man named d'Artagnan after he leaves home to travel to Paris, to join the Musketeers of the Guard. D'Artagnan is not one of the musketeers of the title; those being his friends Athos, Porthos and Aramis, inseparable friends who live by the motto "all for one, one for all", a motto which is first put forth by d'Artagnan.
The story of d'Artagnan is continued in Twenty Years After and The Vicomte of Bragelonne: Ten Years Later. Those three novels by Dumas are together known as the d'Artagnan Romances.