Dover Publications specializes in low cost books, and I've been a fan since high school when "low cost" was an especially big deal. They are still a mostly paper-based company, but they have an expanding range of ebooks.
They are currently having a 79 (US) cent sale on ebooks. Most of these are classics, and may be available elsewhere free, but the books I've bought from Dover were well formatted and some of the collections of poetry, literature and philosophy might be hard to find.
http://store.doverpublications.com/e...al.html#loctop
As I said, they're still mostly a dead-tree business. When I got an email receipt for my last ebook order it did provide an estimate of shipping time and that I could expect it to ship by "Fourth Class Book Rate." Of course, by then I had already downloaded the files.