I'd go with anything by Ken Krenzel. He's got some quality visual, modern-looking magic, but for some reason, maybe because his books aren't sold on dananddave.com or Ellusionist or whatever, he never seems to get a mention.
I'm a big Krenzel fan, can't wait for his new book.
Close up Card Magic isnt really that unknown .. Perhaps the most read card magic book in the 60s-70s
Don't know why the focus on PDFs specifically, not to mention that "little known" is highly subjective. If you mean "mainstream", I'll go with Best of Osmosis by George Mbride, and other Scottish cardmen ( more known: Peter Duffie ).
On the DVD department, can't think of any really, since there's so much crap outt here any good DVD immediatly gets hyped. Bob White's palming vid is awesome.
Saw a post about David Harkey's Ah-Ha! above, not only its very cool, but his other-hard-to-find-book, Simply Harkey, is the hottest book I own. I love and collect everything Harkey puts out ( matter of taste, some people don't like his material ), I wasn't aware he got into the ebooks thingy particularly with Ah-Ha!
Cheers,