Nice article Andy!
Since I am a Bibliophile I normally don’t have budget for books. Along with technical books I also read fiction and other kinds.
One thing I religiously follow is reading at least one article from this site. That way I keep updated with the current world.
Reading is one of the rare things where ROI is very high.
Also books in Indian sub continent are very very very cheap! We get subsidized books. So there is really no need for a book budget, you just need to have an interest in reading.