While reading my e-mail @ gmail.com, I noticed an ad saying, "Ebooks for PRS 500/505 -
www.bltcpress.com - Well-crafted classics in LRF format No digital rights management", so I hopped over to see what they offered. So far, they have 33 titles, all classics (i.e. copyright-free), each priced at 1.99 (USD). They do offer free book, under "Free Title of the Week".