..."Island in the Sea of Time" by SM Stirling. Premise is that for unknown and unknowable reasons, an ellipse that included Nantucket island and a sail-powered Coast Guard training vessle full of cadets are sent back in time by 3,000 years. The first concern is feeding the population through the upcoming winter. The next is making sure that technology is not lost and their civilization thrives. Of course, there are bad guys. It was a very good book with lots of libertarian themes. You would love it.

I recall that John Ringo wrote a novel named something like... oh heck why be lazy: "There Will Be Dragons". Takes place in the far future where insanely advanced computing and technology support a dissipated life style. The computer goes down and people have to learn to support themselves. Roll playing gamers, CSA types, Renaissance Faire enthusiasts, craft hobbyists, and amature historians come to the rescue. Ummm... the types of rescuers in the previous sentence don't mean exactly the same thing in the far future that they do today. For instance, a RPGer uses something like a holodeck and he must be proficient in swordplay before he should consider taking on an orc. Aparently, it's the start of a series, so I should reread the first one and get the other 3 that are now available. I did enjoy it.

(Again) of course there are bad guys. I recall that they used the Roman legionaire model to train their troops. I believe that there were some technological premises that forbade gunpowder powered weapons and permitted some (scientifically supported) fantastic weapons and beasts. A lot of the premise is designed to support a fantasy setting in a perfectly rational and scientific universe.