The Nintendo 3DS was supposed to see an e-Book service this month, called Bookstore Anywhere, developed by Japanese company, Librica. This app has now been delayed and will be released at some later point in the future, Librica have announced via their website.
The Bookstore Anywhere app is in development for the Nintendo eShop. When it launches, it will be a free app and will allow users to download manga, Japanese manga magazines, and eventually even light novels and regular magazines.
Librica say the delay is to facilitate further improvements to the Bookstore Anywhere app, and that they will announce a new release date for the app at some point in the future. You can find details of the original announcement here.