I suggest the 20-page paper "A dialog on quantum gravity" by Carlo Rovelli, available here:
http://lanl.arxiv.org/abs/hep-th/0310077
This represents a chapter in the ongoing string theory vs. loop quantum gravity war that those who follow modern physics may be aware of. Rovelli is a loop quantum gravity theorist, and the paper is in the format of a conversation between a fictional graduate student and professor, debating over the relative merits of the theories.
There is no math, but the language used assumes familiarity with modern physics concepts. E.G. you should know what the standard model is about, and why "perturbation theory" is important. If you're up for it, you'll definately gain some interesting perspective on why there are opposing camps in theoretical physics these days that don't really seem to like or understand each other very much.
And, of course, it's free and only 20 not-very-dense pages.