Not that the dictionary next to my bed isn’t working and not that I was going to stop reading DFW because he makes me work, but:
Touch and hold any word to look it up in the built-in dictionary or Wikipedia, or to search for it throughout the book and on the web.
Apple – iPad – Buy and read books like never before | via Apple.com
I also wonder if this is going to make it easier for my wife to sleep while I read in bed.
Mine’s on order, by the way…