For one, where most of this series takes place in the Victorian or Edwardian eras of the late 1800's and early 1900's, Miss Amelia's List is firmly set in the Regency, specifically 1815, just after the end of the War of 1812. I believe this is primarily because, instead of deciding to retell a fairytale like the majority of the Elemental Masters series, Lackey decided to pay homage to Jane Austen. I must confess, I'm not well read enough on Austen's works to say that this novel is a reimagining of any particular work of hers, but if I were forced to say Miss Amelia's List was a reimagining of any particular book, I would have to say Sense and Sensibility, though I would bet more strongly that Lackey was inspired by Austen's work in general, rather than a particular piece.
Given the book's inspiration, one of the novel's other big differences when compared to the rest of the series is the general tone and the overall conflict of this book. Miss Amelia's List feels more like a slice-of-life story with Lackey's existing world-building at play. I'm not going to go so far as to say this is a bad thing, but it very much feels different, so anyone expecting Lackey's normal formula regarding this series should know that isn't the case here.
Miss Amelia's List follows two North Carolina ladies, Amelia Stonehold and her cousin, Serena Meleva, as they arrive in London with the hopes of helping Amelia's brother, James, establish their family business in England now that the war is over and trade can resume. It seems that the Stonehold estate's farm produces some well-respected textiles and dyes, and the family is hoping to expand their business even more in the coming years.
Amelia, who would obviously be recognized as neurodivergent in today's society, is focused on the tasks ahead of her, and to keep everything straight, she maintains a list. Her tasks include helping James establish himself in England; find a property for James and the business to gain a foothold; and, if possible, find suitable husbands for both herself and Serena. Of course, each of those items come with their own sub-lists and conditions, and while the business has a lot of specifics, so does her list of requirements for courters.
The biggest condition for potential suitors is that they must be Mages at least, though Masters would of course be better. Amelia herself is an Earth Master and her ability to channel means she will be a benefit to whatever land she inhabits, but Serena is her own special case. Not only is her cousin a Fire Mage, but she is also a shifter with the ability to turn into a leopard, but given the prejudices against that even in magical circles, that's a detail those in the know will have to keep on the down low.
While Miss Amelia's List does include an antagonist that ends up being the final confrontation in this book, that entire aspect feels almost like an afterthought, as if it was put in there because Lackey felt like readers wouldn't want a book that was entirely the slice-of-life tone that most of the book represents. In fact, besides some rude comments and snide remarks, the villainous nature of the enemy seems to come out of nowhere, with very few seeds of his eventual nature laid out in earlier parts of the book. Instead, the main conflict that Amelia and her family face throughout most of the novel seems to be the world events that happened in 1815, namely that of Napoleon's escape from the island of Elba and the volcanic eruption of Mount Tambora, which will lead to the Year without a Summer.
During the Hundred Days conflict regarding Napoleon's re-taking of France, the people of England are on high alert and Amelia will find her efforts to mark items off her list tougher than expected, but when her Earth Master senses tell her of the volcanic eruption in the Dutch East Indies and the fact that the coming summer will not be warm enough to produce crops, she does whatever she can to warn those that will listen and fortify the farming land in order to prevent as much starvation as possible.
Overall, I didn't dislike Miss Amelia's List: Elemental Masters - Book 17, it was just a different style for the series and I don't begrudge Lackey for going in a different direction. I will say that I wish I knew how the book would feel without the final conflict, or if that final conflict had a slower build up. As it is, those events take place in the last chapter and are as quickly resolved as they appeared. The result is a bit of whiplash that leaves a sour taste at the end of the book. Again, I'm not well read in Austen's works, but if Miss Amelia's List was meant to pay homage to those novels, then it might have been nice to keep that tone all the way to the book's final pages.
All that being said, while I wouldn't rate Miss Amelia's List: Elemental Masters - Book 17 as one of the best books in this series, it isn't amongst the worst either. I did enjoy a majority of the novel and it was different. Any fan of Lackey's or this series should still read it, but go in knowing that it is different, both in setting and tone.