what programming languages do you teach? I ask because, I remember now back to when I first really started trying to program, and I think it would have been great to get introduced to interesting code bases back then. So guess, I'm just looking back now and will recommend what I wish I had had, maybe some of it help:)
As a teen, I fumbled around for a while before discovering linux and open source and that good feeling you get when you download the src and start perusing and firing up your debugger. Having said that if you teach js, I'd highly recommend dojo, underscore, I guess most c /c++ might be too advanced but if not Webkit, Redis, and glib are clean fun code bases and dissecting Lisp / Emacs was a blast. As far as answering you actual question goes, I really liked Gödel, Escher, Bach back then, also thinking recursively by Roberts. The only "technical" book I enjoyed reading was Modern Operating Systems by Tanenbaum ( don't know what current editions are like, the roughly 2000-2001 version was great though). Its was simple, very clear, humorous, and a gives a great overview of how the os works.