Adobe Digital Editions is Adobe's official eBook reader.
Adobe Digital Editions is very simple and basic but allows you to browse an elegant library of texts and read them in comfort. Adobe Digital Edition lets you add new items to your library and distribute them in different categories (known as 'bookshelves'), read a selected book on the screen with several viewing options, insert bookmarks in your book and easily move around pages.
Adobe Digital Editions is also meant to work together with online ebook stores and public libraries, enabling you to manage the books you buy or borrow directly from the program. You need to find these resources by yourself though, because Adobe Digital Editions only provides a few sample books to download.
Adobe Digital Editions is a handy ebook manager with a nice simple interface although it is very basic - there's even no full screen mode - and it only works with two formats: PDF and ePUB.