The Fictionwise free book is in .lit format. (And they also offer a paid version; the freebie may be a programming glitch.)
Looking around to see if it's offered at other sites, I found another book by the same author,
Vision, free at ereader.com. (EReader format. Seems to say it doesn't need an unlock code, but I'm not on a machine that reads eReader at the moment so I can't check that.)