Somewhat in the spirit of a challenge or at the very least a non-contest I propose the following; citation of the oldest still useful programming book you own or can put your hands to. This of course if my sly way of getting (hopefully) a list of what I might be missing from my own shelves. To start things off, here is a real contender:
Probably one of the clearest introductions to parsing and related details I've ever read. Should you feel compelled to acquire this classic for your very own, note that I just upgraded to a hard back plus dust jacket for the princely sum of $13.00 including shipping--- spine was cracked and pages were scattered about in my newer copy from Springer-Verlag.