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.
The whole famly loves the skippjon jones books. They are hilarious and the narration is great!
Judy Schachner's voice and accents are too fun! My 4 year old and I love this entire series. A bath time favorite!