Print/Ebook:
Amazon: http://bit.ly/VisionofFireAZ
Barnes & Noble: http://bit.ly/VisionofFireBN
Indiebound: http://bit.ly/VisionofFireIndie
iTunes: http://bit.ly/VisionofFireiTunes
Google Play: http://bit.ly/VisionofFireGP

Audiobook:
Audible: http://bit.ly/VisionofFireAud

In the UK:
Hardcover
Kindle Edition
Audio CD
Paperback (will be released on June 18, 2015)