The Elegant Universe is the best possible introduction to superstring theory, especially for a layman (as far as mathematics goes). Brain Greene uses fitting illustrations, and very good analogies, to make complex points easily understandable. He warns you before going into anything where he might lose those without great interest in details, and tries to make sure that he doesn't bog one down with such details. One thing I really appreciated is that Prof. Greene explains the seeming incompatibilities, before saying anything about how string theory resolves them. He makes sure that you understand the inconsistencies, so that you can really appreciate the resolution - given by string theory.