Fevre Dream by George R.R. Martin

Abner Marsh has had his dearest wish come true - he has built the Fevre Dream, the finest steamship ever to sail the Mississippi. Abner hopes to race the boat some day, but his partner is making it hard for him to realise his ambition.

Joshua York put up the money for the Fevre Dream, but now rumours have started about the company he keeps, his odd eating habits and strange hours. As the Dream sails the great river, it leaves in its wake one too many dark tales, until Abner is forced to face down the man who helped to make his dreams become reality.