A Constant Love (by Sophie Turner) [and A Change of Legacies]

This is a Pride and Prejudice continuation story that was recommended on Ask Metafilter, and I thought it was really well done. I actually have tried to get into a lot of the continuations, but have never gotten very far into one. This one sucked me right in -- the original characters are delightful, the voice is convincing, and there is an added level of historical detail that I really enjoyed. (For instance, I hadn't known about the practice of chalking ballroom floors.)

 I've moved right into the sequel, which I'm not sure is up on Amazon yet -- but you can find it on AO3. Which means yes, I suppose this is "fanfic" -- but the line there is a bit blurry, considering that all the traditionally published continuations are also kind of "fanfic," and some of them are notoriously bad. Don't let it put you off if you enjoy this sort of thing. I don't usually put book-length fanfic on my reading list, even though it is book length and some of it is quite good. But this is "literary fanfic" so I guess I'm counting it this time.

[Edited to add: I already tore through the sequel, A Change of Legacies. The author is reportedly planning five more books in the series, and each one is meticulously researched. As one of the characters might say, I enjoyed the sequel prodigiously well!]