There are multiple apps around that are designed to manage all the interesting stuff you want to read. There are read it later services, like Pocket or Instapaper, which allow you to save articles you find on the internet but don't have time to read. For books there's obviously iBooks, and the Kindle app as well. dotdotdot is a free app which attempts to unify these two different reading apps into one, to provide one go-to place for all your reading.
The idea itself is great. Theoretically it eliminates the need to switch between apps when reading web articles or books, although personally I rarely read both in one sitting. Webtexts are easily imported by copying and pasting the URL of the article into the app, or using the built in web browser. Ebooks are slightly harder to import, as there is no ebook store. Instead, you upload your ePub files to Dropbox and import them from there, which is a fairly neat solution.
With your articles imported, you can organise them into "lists" of texts. You can combine both books and articles in one list, and work through them easily. This organisation function is really useful to find a specific article, or to read about a specific topic when you get a free moment. dotdotdot also makes reading more social. You can connect with friends and see what they're reading and share comments and highlights from what you're reading. This enriches the overall reading experience, promoting discussion. Your highlights are also archived if you wanted to come back to a specific fact or quote, allowing you to find favourite parts of a text quickly.
Of course, a reading app is pointless if the experience of reading it isn't satisfying. dotdotdot does deliver on the reading front, providing a large and legible serif font which allows you to flip through your pages quickly. However, if serif isn't your thing, you're pretty stuck as dotdotdot lacks any customisability at all, which may put off a lot of users who are pickier with their fonts.
Dotdotdot is available on the web, iPhone and iPad, so you can read in any situation. However, this feature is where dotdotdot falls down, as the iOS client doesn't sync with the web so you have to find your place each time. As such, dotdotdot isn't truly cross-platform just yet, but I believe it is in the works.
Overall, dotdotdot is not a poor reading client by any means; it certainly fulfills its goal of unifying the reading experience. However, the lack of an ebook ecosystem, such as that of Apple or Amazon makes it slightly harder to use for those who don't already have Dropbox. Certainly for me, dotdotdot has not replaced my combination of apps to read both books and articles, though I may give it another go if the syncing issue gets sorted.