The precursor to Brian Greene’s excellent The Fabric of the Cosmos, this is a good introduction to the current cosmological favourite, and attempt at linking general relativity and quantum theory, (super) string theory. Written it 1999, it has dated a little, but still gives a good laypersons view of string theory and its relationship to the two pillars of 20th century physics.
It’s a shame, in a way, that there’s so much overlap between this and Greene’s more recent book – so much so that unless you want to go into string theory in considerably more detail, you might as well go for The Fabric of the Cosmos, which has a lot more detail on those fundamental essentials, relativity and quantum theory, and does the job a little better.
However this shouldn’t undermine the fact that this is a very good book on the attempt to produce an overarching theory for the fundamentals of space, time and matter. Greene is always approachable (if occasionally irritatingly folksy) and makes a good effort of explaining complex concepts in a way that is still mind boggling (he can’t help that – it’s the nature of the beast), but possible to get your mind round.