There's a whole series of novels, the 1632 series started by Eric Flint and the Grantville Gazette anthologies (something like 30 ebooks!) about a small West Virginian coal town that gets thrown back to 1631 in central Europe, right in the middle of the 30 years war. They have a 1911 Encyclopedia Britannica that becomes property of the state and is frantically needed to inform them all who is ruling what and why back then, and what they will have to cope with. It is referred to so extensively, it has become a kind of character in the stories in its own right.
They went with the 1911 edition for 3 reasons:
- It really was on the shelves of the high school library in the real town the author used as his model for Grantville.
- It is one of the best encyclopedias ever for older history details, with lots of mention of things happening in the 17th century. Newer editions had to prune that out to make way for the 20th century's explosion of new things.
- It is old enough, the copyright has completely expired.
It is a very interesting use of unbelievably good material to build an alternate universe.