I went to Audible and searched: "The Cinder Spires: the Aeronaut's Windlass". It found THE BOOK (give me the book), so I log into Audible and it says: "We're sorry. Due to publishing rights restrictions, we are not authorized to sell this item in the country where you live." That sucks I cannot pre-order yet, however it does kind of hint that it will be available at some point.
If you want the spectacularly vague page: http://www.audible.com/pd/Sci-Fi-Fantasy/The-Aeronauts-Windlass-Audiobook/B00XKCNARK/ref=a_search_c4_1_1_srTtl?qid=1432580337&sr=1-1