I found out that Father of Fear made a list of "11 Heart-Pounding Thrillers About Kidnappings and Mysterious Disappearances" made by the Ezvid Wiki team! Check out the link and their video below to see it for yourself and take a look at the other books and movies on their list! Maybe you'll find something to tide you over until the next book comes out ;).

https://wiki.ezvid.com/m/11-heart-pounding-thrillers-about-kidnappings-mysterious-disappearances-LUsZFodlv7NVO