Harry Turtledove 
Liberating Atlantis [EPUB ebook] 

Frederick Radcliff is a descendant of the family that founded Atlantis’s first settlement, and his grandfather Victor led the army against England to win the nation’s independence. But he is also a black slave, unable to prove his lineage and forced to labour on a cotton plantation in the southern region of the country. Frederick feels the colour of his skin shouldn’t keep him from having the same freedom his ancestors fought and died to win for themselves. And when fate presents him with the opportunity to throw off his shackles once and for all, he becomes the leader of a revolutionary army of black and red slaves determined to free all of his brethren across Atlantis.