According to the New York Times, in Japan, manga on mobile phones is considered a success at a time when print sales are moving downward.
… some analysts are calling the cellphone “the savior” of the form and a necessary kick in the pants for a sagging industry.
It’s estimated that publishers get 10% of their revenue from mobile sales. Pluses for the format include convenience, immediate satisfaction, and privacy (the most popular titles are “adult-oriented ones for women”). And I was surprised to see praise for “the graphics, [with some] saying manga looked especially good lit up against the dark screen of a cellphone.” But remember, Japanese cell phones are more advanced than others, with high-speed networks covering almost 100% of the country and advanced software.
More detail on the female audience is provided:
The romance- and sex-filled manga — known as shojo manga — are read by women in their 20s, Mr. Tashiro said. In fact, about 70 percent of cellphone manga readers are women, he said.
I’m not sure they really meant shojo; josei may be more accurate, but the term hasn’t got as wide-spread penetration here. The article continues with predictions that mobile manga will replace print. (I doubt it, especially since male readers are less interested in online reading.) Publishers are also sticking to old models, with older titles, already out in print, being the ones translated to mobile.