Ruby is a young thief in training in an alternate 18th century Europe, one full of alchemical magic, working hard to master lockpicking and useful skills. She's also happy to sail with her father back and forth to the Americas, on what might appear to be a pirate ship, but actually is a more ordinary smuggler. But the voyage that sets the story in motion is far from being ordinary when their ship is perused by an admiralty vessel, on which is one of the King's Reeves--the most deadly fighters there are. The foppish boy, Athen, a passenger on the voyage, proves to have useful fighting skills, and Ruby's own skills at hiding are useful too, but the rest of the crew, including Ruby's father, are taken prisoner. Ruby, Athen, and the Athen's servant claw their way in a leak rowboat to Philadelphi [sic] (marvelously transformed by alchemy).
Ruby knows she has to find her father again. But she herself is still being perused by the Reeve, and Athen shows himself to be an uncertain ally with his own agenda. As the danger to Ruby becomes ever sharper, it becomes clear that she herself is the prize being hunted for, though she doesn't know why until she meets an ancient alchemist of extraordinary power, who finally gives her some of the answers to the riddle that's been making her live so extraordinarily difficult.
This is one for those who likes swordplay, and chemical magic play, and pursuits through strange places that never existed. It wasn't quite to my own taste, because when the main character is deeply confused throughout most of the book, and everything goes wrong repeatedly and there is no safety, I empathize too much, and feel confused and unhappy myself, especially during the beginning third or so, when I haven't had a chance to learn to care about the characters yet. But Ruby and the cast of supporting characters are all prove to be interesting and engaging, and the alchemy is fascinating, and the second two thirds of the book went by rapidly, holding my attention very nicely indeed.
Note--I am always rather interested in how Native Americans exist in alternate histories such as this set in the Americas. We don't get to learn much about them in this book; there's just one brief mention that they are there, outside the city, but that is a smidge better than nothing....The main characters are all white, though there are a few side descriptions of people who aren't.