YES. I PLAN ON DOING IT AGAIN SOON. I HAVE ALREADY LISTENED TO RIVER AND STAR'S STORIES TWICE. I CATCH THINGS I MISSED THE FIRST TIME THRU.
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.