Alexandre Dumas wrote over 277 volumes over his lifetime. He didn’t write them alone, however, he collaborated! Chief among his collaborators was a history teacher named Auguste Maquet.
Dumas fathered two illegitimate children by two different mistresses, and then married yet another mistress.
Dumas died broke. Auguste Maquet, the man who collaborated with Dumas on most of his works, died very well-off. He declined attribution for his work in favor of high compensation.
The 1973 movie version of The Three Musketeers is infamous for when director Richard Lester decided he had enough material for two films and released a second installment entitled The Four Musketeers. He neglected to pay the actors, who brought him to court and eventually won their case.