How many books does the series The Missing have in it?

There are three books in the "The Missing" series by T.J. Klune:

1. The House in the Cerulean Sea

2. Under the Whispering Door

3. The House in the Cerulean Sea: A Novella Collection

Note: "The House in the Cerulean Sea: A Novella Collection" contains several novellas set in the world of "The House in the Cerulean Sea," but it's not a full-length novel.