Just bought one and it worked just fine.
edit: it explicitely says it's only for e-books and videos.
Re:Tell HN: Save 60% on all O'Reilly E-books
by bretthoerner on Monday November 29, 2010 @09:59AM
(#1950443)
40% off print here: MYPF4
Via: https://twitter.com/#!/stuccharlton/status/9185592818536448
Not sure about the US-only bit, though.
no joy for me.
Edit: works for ebooks only for me, not for printed versions. I'm outside the US, so that may be a factor?