There are more books in the public domain than you would imagine, but it can be a real pain having to go dig for them. Voluminous lets you find free books straight from your desktop.
The application allows you to search the net for free books, store them on your Mac and even save them as PDFs. You will also have a large choice to choose from, as Voluminous is not limited to books in English but offers many others in all sorts of languages including French, Spanish and Portuguese.
You can browse books by categories, like philosophy, law or education and use the search function at the top right of the program window. I would not recommend this last one though as it runs a little slow.
Voluminous offers a 'Starting Points' section, which is mainly a selection of famous novels, a good way to get started if you do not know what you are looking for. 'Latest Additions' also lets you monitor all the books that have just fallen into the public domain and get hold of them.
Once you have downloaded a book (by double clicking it), you can save it as PDF, view in full screen or read inside the program window, using one of nine different themes.
Despite the slow search function, Voluminous is very useful to search, store and read books that have fallen in the public domain. Recommended if you are into literature.