There are 4 books in the Mermaid Mysteries series.
The Mermaid Mysteries series does not have a new book coming out soon. The latest book, Melody and the Sea Dragon (Book 4), was published in March 2012.
The first book in the Mermaid Mysteries series, Rosa and the Water Pony, was published in July 2011.
The Mermaid Mysteries series primarily falls into the Mystery genre. This chapter book series was written for ages 7-10, but some older readers may still like to read these books.