It is both simple and intuitive to use: in the search bar located in the main window, you'll enter the name of the book you're interested in and hit 'search'. Alternatively, you can enter the book's ISBN to go directly to it.
Any book you find will be marked with one of three different tags: red for those you won't be able to read, yellow for those that include a preview of a few pages, and green for those you can read in full (Don Quixote, for example).
GooReader is an application that should please reading buffs, although you do have to be comfortable reading on your computer screen.
The free version will not permit you to convert books to PDF format.