There are 3 books in the City of the End: The Underwater City series.
The City of the End: The Underwater City series does not have a new book coming out soon. The latest book, The Mermaid Queen (Book 3), was published in November 2016.
The first book in the City of the End: The Underwater City series, An Old Enemy, was published in November 2016.
The City of the End: The Underwater City series primarily falls into the Thriller genre. This middle grade series was written for ages 8-12, but can be enjoyed by older readers as well.