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.
loved it wish 2010 was available needed that too complete the series, of Odyssey not available on Audible
Arthur you are a legend. RIP while your legacy lives on. great book, one of the all time greats.