Quick-take: Light-hearted pirates.
Tress is a girl from a small island that is trying to save her friend. She has spent her whole life on the small island (don't remember her exact age.... maybe 16?). She leaves to go save Charlie, and adventure ensues.
Most of the book takes place on a pirate ship. Fantasy authors love writing about pirates for some reason. I know nothing of proper nautical terms, but I will assume it is reasonably accurate.
Brandon Sanderson does his typical world-building. He has various realms that he drops his characters in and designs fantasy rules for the surroundings. I am a Sanderson fan, but I do not know his different relms. This one involves something called spores. When you get them a wet, an interesting effect occurs. The seas are actually spore seas, and the ships sail on them.
The book emphasizes that Tress is just an unremarkable girl who's only career up to this point has been washing and baking. Calling her "unremarkable" is vastly underestimating her. She is very clever, brave, and excellent at scheming. I am taking a point off my score simply because Tress is just too good. She is reading and adapting schematics based purely on intuition that she shouldn't have. I don't believe it.
The book is threaded with humor, and it does OK. Some of the humor is based on "random", which I am not much of a fan. However, the delivery and timing is done well, and there is a decent amount of situational humor which I do like.
Score 5/5. I removed a point earlier, and now I am adding it back. This is full enjoyable story in a single book. Books that are complete stories can be hard to find in the fantasy genre.