@DoubleD iirc they made studies about this for GPS navigation and female voice were found more suitable, hence this is what we have everywhere nowadays. man's voice, i think, was considered too commanding or something like that. as for audio books, that depends on personal preference. but also on how good the voice actor is. it is indeed acting after all, not just reading in monotone.
@Justicar Interesting information about the proliferation of the female voice. Maybe I'm secretly wishing for widespread Taliban restrictions about females talking in public.