I don't know the reasons myself, but that (Girls will read boys' stories but boys won't read girls' stories.") was certainly a phenomenon that the librarians at the all-boys' school where I used to teach were constantly beating their heads against. (Even though, being an all-boys school, it was in many ways *less* gender-role-segregated than the norm -- performance of masculinity is totally different when there are no girls around to perform for.)