
The Right Man for the job One moment Conrad Schwartz was a hungover hiker in the mountains of modern Poland, the next he was running for his life from an angry Teutonic Knight. At first Conrad just thought he'd stumbled across a mad hermit. But several days of ever stranger events convinced him that he had somehow been stranded in 1231 A.D. And that meant Conrad had to turn Medieval Poland into the most powerful contry in the world. Otherwise the Mongols were destined to detroy it--in just ten years!
[I only liked the first four books, but that's enough to cover the original story arc]
Also, I would highly recommend "The Cross Time Engineer" series as it's this same scenario but works through how he's able to apply his modern knowledge as leverage to work up from a boatman earning pennies to running the country.
1 - https://www.amazon.com/Cross-Time-Engineer-Adventures-Conrad...
I recommend the series as it's absolutely fantastic from an engineering perspective, but also kind of horrifying from a culture one.
1 - http://www.amazon.com/Leo-A.-Frankowski/e/B000API2VY/ref=dp_...
While it's surely not wholly accurate, everything related to the material science and technology level is at least plausible.
http://www.amazon.com/Cross-Time-Engineer-Adventures-Conrad-...
There have been some books that explored the idea - I recall a series "The Cross-time Engineer" which isn't actually that great, but does have some obvious engineering knowledge.
One thing I do think it gets right is that if you're sending someone back in time to change the past, you do NOT send a scientist, you send an engineer or a mechanic with the Handbook of Chemistry.
