My love of mathematics accounts for a couple of sets of letters after my name, so I feel that I'm on 'home territory' here.
The problem with seeking out non-populist books in mathematics (and probably in astronomy and astrophysics as well) is that most developments in mathematics don't fill an entire book. They're usually represented by a short paper, taking no more than a few pages, in a specialist magazine.
If someone was seeking to find a suitable present for me, I hope that they would be looking at something like 'The Art of the Infinite'. Yes, it's fairly populist but it seeks to explore the connection between mathematics and 'real life'. It's a tenner for the paperback or 20 quid for the hardback:
http://www.penguin.co.uk/nf/Book/BookDisplay/0 ,,9780141008868,00.html
However, what I'd really like would be a subscription to 'New Scientist' magazine. �20.50 for 3 months (13 weekly issues) or �82 for a year (51 issues):
http://www.magazine-group.co.uk/magazine-group /categories/general-interest/3547/new-scientis t.thtml
Chris