If you are the kind of person that judges a book (and he who’s reading) by its cover, well, you might have a hard time doing so in Japan. Japanese people read a lot while commuting in subways and trains (that is if they are not playing with a PSP, fiddling with the mobile phone or listening to their iPods using HUGE headphones). I do a lot of people-watching and I noticed that most of them have the book’s cover protected by either paper, cloth or even leather. In the first case, when paper is used, it is almost always provided and folded by the bookshop where it was bought. In this way they offer the service of protecting the book cover and the reader’s privacy. As a counterpart they obtain brand visibility, because the shop’s logo or some other easily recognizable sign is printed on that paper.
I’m not sure whether the egg or the chicken came first and that is the shop wanting to make a subtle branding campaign or the book user wanting to hide what she’s reading (be it hard philosophy or dirty hentai manga). The point is that you can hardly tell what someone is reading on the metro but you can accurately state where it was acquired.