A couple years ago, I started to have an idea for a novel. It wasn't the first such idea; I have several kicking their way around my head. I don't have time to write more than a chapter or two in brief spurts, but I let the ideas percolate and refine. Eventually, I will have that time, and hopefully the ideas will be timeless by then. Or something.
But at least one of those ideas is now out of the running, thanks to S. M. Stirling's Dies the Fire; he has simply done it, and done it well enough that I doubt I will follow down that particular path.
What was the idea? Simple: take the modern world as it is today, or close to it, and postulate some Event that prevents much of modern technology from functioning. It doesn't matter exactly how it works; what matters is how humanity copes with the results, which will effectively revert the world to the middle ages. The important things that make up modern civilization, for this purpose, are: electricity (computers, power delivery), explosives (including gunpowder and gasoline), and steam engines.
My idea was primarily concerned with firearms, and the effects of their removal: without them, the human race is back in direct competition with animals and each other by strength and speed. By removing firearms from the equation, which act as a remarkable equalizer in allowing smaller, weaker, and relatively untrained human beings to defend themselves on an equal footing with large trained soldiers, the world is forced to revert to feudalism. This has the obvious consequences on the civil rights of women, racial minorities, and those who simply aren't good at personal violence.
Stirling explores the idea very well, with a number of distinct and interesting characters he follows from the first moments after the Change through the formation of new social structures and the first season's harvest. Psychologists, anthropologists, fantasy readers, survivalists, SCA members, even wiccans will all find something interesting in this book.
Kudo's to the author for telling it first, and possibly better.
There's a sequel out, The Protector's War. It's sitting on my to-read shelf right now.