I feel that the title The Book of Negroes to be appropriate to the story. It is deliberately referring to the historical document of the same name. If this is the title the author chose for the book, there is most certainly a considerable reason - or many - and we should respect that. The content of the book itself is very explicit; anybody reading it should be able to cope with considered "inappropriate" words, phrases, and circumstances. Censorship as a practice is acceptable, but it's not fair to criticize and try to change original works. The book burnings are extremely inappropriate and even offensive. As already explained, it's quite evident that the author isn't being racist by intentionally throwing the word "negroes." However, if need be, I would suggest the following alternative names:
"Pink Water"
"Dark Nights, Dark Days"
"A Lion Called Injustice"