I'm a librarian who loves anime, manga, and reading a wide variety of genres.
The Vast Spread of the Seas is the only book in this series that I've liked somewhat less upon rereading it. It did have some good moments, though. I loved the bit where Rokuta/Enki made Shoryu carry him when they were reunited. I just wish less of the book had been a slog.
Next up: Skies of Dawn, the last book in the series to be translated into English, and the only one I've never read, although I've seen the anime and therefore have some idea of what's going to happen. Yoko gets to be awesome!