Originally Posted by pholy
In the Kobo (using ADE) a font-family in a body selector gets overridden by the reader software; I wasn't aware of this on the Sony. Try putting the font-family in a p selector, to see if it works there.
OTOH, I seem to recall that if ADE detects any errors in the css file, the entire file gets ignored. I can't think of any css verifiers off-hand, unfortunately.
That's a bug in Kobo's implementation of ADE. Most ePub from publishers put the font family selector into the body. This does work fine with Sony Readers.