I have installed some books from http://www.epubbooks.com/ They provide a selection of un-DRM'd ebooks in epub format. Currently I'm reading some stories of H.G. Wells.

I also have tried to buy a DRM'd Stephen King ebook from a webshop here in Switzerland. But FBReader cannot handle it (well, it can open it but it displays a blank book). So for now I'm staying away from DRM'd ebooks.