Recently the New York Times ran an article about Manga for Girls. In other words: shoujo manga. Even though I might nit-pick on a few points, it's a pretty solid article.
Shojo - the word means girl in Japanese - frequently involves a lovelorn teenager seeking a boyfriend or dealing with situations like entering a new school, being bullied or trying to break away from a clique. There are also action stories featuring girls in strong roles as scientists and samurai warriors. (The shojo genre has been called "big eyes save the world," after the characteristic drawing style of girls with saucer-shaped eyes who are sometimes endowed with supernatural powers.)
But parents and teachers, who are sometimes happy to see teenagers reading just about anything, might be caught off guard by some of the content of the girls' favorite books. Among the best-selling shojo are stories that involve cross-dressing boys and characters who magically change sex, brother-sister romances and teenage girls falling in love with 10-year-old boys. Then there's a whole subgenre known as shonen ai, or boy's love, which usually features romances between two impossibly pretty young men. [NYTimes: Manga and Girls]