This was a pleasant read that I finished in one evening. I liked the general plot idea. In the beginning, Darcy suffers an accident soon after the Disastrous Hunsford Proposal, the Colonel finds his letter to Elizabeth, and assumes there is an attachment between them. But when Darcy wakes up from his unconsciousness he does not recognize Elizabeth and assumes that he's engaged to Anne. Which pleases Lady Catherine to no end. Elizabeth feels guilty because she is sure that the accident happened because of their argument. This set up a very interesting beginning.
However, thereafter things are largely business as usual, and the amnesia stops having much of an effect. There is quite a lot from canon, both direct quotes and plot elements. The characters are able to remember many past conversations exactly verbatim... In my opinion, a little more in author's own words wouldn't have gone amiss. If I want to read Austen's exact dialogue of Lady Catherine's confrontation with Elizabeth I know where to find it in Pride and Prejudice.
The plot jumps and skips quite a bit in a way that may leave the reader with a sense of wait-what-just-happened, like there is some missing information, or information that is not supplied in the chronological order but as an afterthought much later. For example, initially we have no idea if or how Darcy extricated himself from the assumed engagement with Anne honourably. Later we find out that Darcy has had some kind of confrontation with Lady Catherine when he leaves Rosings but this is reported as a second hand reference and we don't know what was said. There's a dramatic death and a property in Scotland that are reported as a sidenote, and a letter from Miss Bingley that we find out about later, when someone talks about it. Lady Catherine receives a letter in a very dramatic manner, saying it has to do with the family honour. But we have no idea who it was from or what it said, although we can assume it had something to do with Lydia's rescue. In the end our dear couple find a mysterious old letter. Which will remain a mystery for the reader, for evermore. (Maybe it was just an excuse for them to talk about Darcy's famous first letter.)
The editing is quite good and the language is very readable.
History nitpick: It is assumed that the mourning period is six months for a brother-in-law. But a quick googling tells you that it was more like six weeks or so.
Steam level: Kissing.