I agree that a good book is a good book, no matter the ethnicity of the author. If a white author can write a book with mainly black characters, making them multi-dimensional rather than stereotypical, then I don't see it as a problem. However, it would be wonderful to see the day when black authors can write books dominated by white characters and have their books accepted in the mainstream. Then we'll know we've made progress.
Black authors are usually forced to write only about black characters, with a few rare exceptions; otherwise, their books won't get picked up by major publis