"Dies the Fire" is the second book I've read by Stirling, and once again the concept behind the story was rather interesting. Unfortunately it suffers from some of the problems his last book had (Conquistador: A Novel of Alternate History). The basic premise is that an event happens that "turns off" all technology, essentially rolling mankind back to pre-gunpowder time. Not only is technology rolled back, but the basic rules of nature that allows for gunpowder, and other forms of energy, simply stop working.
So obviously the world goes to hell pretty quickly, and the story covers the lives of some of the survivors as they attempt to rebuild civilization. As with Conquistador, I find the major problem I have with Stirling is how verbose he is (a problem I have myself). In Conquistador he wasted numerous pages on talking about how pretty the land was (yawn). In this one he spends quite a bit of time on things that just really detract from the story.
I do think it is worth picking up (I'm adding the second book to my wish list soon), but you will need a bit of patience to get through the slower parts.