I took a course on HCI (at Imperial, Professor Robert Spence) and it _was_ the first 'assigned' reading, definitely recommend - and it's actually a pretty good stocking/'secret santa' present this time of year for anyone even idly curious about things and how they work.

I'd also highly recommend Spence's own book: Information Visualisation. I don't work in HCI/UX at all, but I enjoyed it a lot; it does an excellent job of showing that it's much more than 'just' (sorry!) artsy design.