Actually Ann Marie Lee did a very good job!
No! I loved the first three audio books and would listen to them more than once, but they changed the narrator and she is horrible.
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.
I would recommend this series however I have only read the first 5 and I'm just starting the 6th. This was not my favorite of the 5.