At the turn of the century, boys' books were full of daring and adventure, while girls' books offered models of mothering and housekeeping. Thank goodness, times have changed.
Nonetheless, boys and girls do tend to read somewhat different books, beginning in middle school, when peer-group pressure becomes so important. Most girls remain quite willing to read a book whose central character is a boy, perhaps because they read well enough to project themselves into another character. Boys, alas, become increasingly unwilling to read any book that has a girl as the central character. Maybe the young male sexual identity is that much more fragile.