Brian Greene's "The Elegant Universe" is the best book on a scientific subject I've ever read.  The first five chapters, which deal with Space, Time, Special &amp; General Relativity, and Quantum Mechanics, are incredibly clear and worth the price of the book alone.  Without using any math, Greene is able to explain the key points of all these topics, and most importantly, to show why Relativity and Quantum Mechanics are incompatible, and why that's a problem for physicists.  He then takes the reader through the various stages of thinking that have gone into String Theory, and it's fascinating stuff!  Greene uses copious examples to demonstrate concepts that are difficult to visualize or grasp, and this is incredibly helpful.  You definitely get a sense, for instance, of what a "curled up dimension" means, through some very clever reduced-dimension examples (not sure if these are Greene's constructions or well-known in the physics world, but they're very clear and helpful).  The going gets a little tougher towards the end  of the book, where the most recent thinking on String Theory and the discussion of Black Holes &amp; the early instants of the cosmos are more complex and tougher to grok straight through.  But even so, they are fascinating and worth the effort.<br>Greene's prose is clear, analytical, and well thought out.  At least a half dozen times while reading the book, I said to myself, "Hmmm, but what about X?" to find a few paragraphs later Greene would write,  "You may be wondering about X.  Well, here's how that works..." To me, this is a sign of a clear thinker and helped make the book even more enjoyable to read.  If you're at all interested in cutting edge physics theory, this is a great book to turn to.