Carole McDonnell has written a review of Writing the Other, by Nisi Shawl and Cynthia Ward. (Link from Locus.) It's a book aimed primarily at writers, and it considers (apparently) the problems involved in writing about characters who are different from yourself in terms of age, class, race, education, et cetera.
Well, I think I'm happy to leave the reviewing of this one to Carole. I don't think, at my age, that I want to read a book which goes on about the 'dominant paradigm'. Neither do I feel much enthusiasm for a book which is recommended 'for schools, colleges, and creativity workshops, and sociology classes.'
On the other hand, for all I know, it might have a transforming effect on your fiction. Take a look at the review and see.