There are 6 books in the Neptune Adventures series.
The Neptune Adventures series does not have a new book coming out soon. The latest book, Red Tide Alert (Book 6), was published in December 1998.
The first book in the Neptune Adventures series, Danger on Crab Island, was published in April 1998.
The Neptune Adventures series primarily falls into the General Fiction genre. This middle grade series was written for ages 8-12, but can be enjoyed by older readers as well.