I found another ebook about Kate Warne, this one oriented to young children. How Kate Warne Saved President Lincoln is beautifully illustrated, and is actually cheaper as a physical hardcover. After summarizing a few of Kate's early detective cases, the book recounts the Baltimore Plot to assassinate Lincoln before his inauguration. I knew most of the story already, but it had some details I did not know, such as Allan Pinkerton making Kate the head of his agency's Washington office. I'm glad such a book exists, because we need to teach our kids about pioneering women heroes like Kate Warne.
I also recently read a historical mystery called Lady of Ashes by Christine Trent. It's about a woman undertaker and her terrible husband who is secretly plotting with his brother to smuggle stuff to America during the Civil War. Some of the characters are American diplomats and spies; they often refer to Washington D.C. as "Washington City." The book goes into real international crises like the Trent Affair, and the Confederacy's efforts to get diplomatic recognition from Britain. The author not only name-drops famous Victorians, but she includes Queen Victoria herself and Prince Albert as characters who meet the titular undertaker. Normally I don't like this kind of namedropping of celebrities, but the book is so full of valuable historical details that I tolerated the liberties she took with history. (My unfinished novel about Sherlock Holmes includes young Mycroft being fascinated by the American Civil War, so knowing what events he might be discussing with his family is helpful to me.)
Anyway, after the smuggling plot, the story continues through the rest of the Civil War, past the assassination of Lincoln. There's a huge train accident, and a second mystery emerges about a real serial killer who fictionally interacts with the main characters. They solve the crime and decide to move to America to get away from all the notoriety. So not a typical detective novel at all, but more like a series of adventures for the heroine. The book is the first in a series, so I think I will continue on with it.