Although I think using two voices can be effectively done, I hate to say that it should be required. I've "read" too many books-on-tape where the actor did an excellent job. I have noticed, however, that most of the books-on-tape I've read have been voiced over by men. Perhaps it sounds better for the men to read both sexes parts by using a lighter voice for ladies than it would be for a woman to try a gruffer voice for men.
Elisabeth
