I had read a few of Michael Grant's books, and short stories. I loved this story and the gone series. The best!
There are many reasons why a book might be unavailable.
Sometimes a book goes temporarily out of print - and sometimes no audio version has ever been recorded. Audible wants to give you the most complete selection we can and we'll keep adding series and filling in gaps as quickly as possible.
Michael Grant amazes me once again. His writing is 👌👌 , and the narrator captures the story perfectly.