Akihiko Yoshida was the main character designer and lead artist on Bravely Default and this book is filled with his artwork.
From the publisher:
Experience the critically acclaimed Bravely Default like never before! Join the game's creators as they send their heroes on a journey to awaken the elemental crystals from all-consuming darkness, and explore the fantastical world of Luxendarc in a whole new way.
* A faithful localization of the original Japanese volume, presented in English for the very first time!
* Features hundreds of pieces of development art and exclusive commentary from the game's creators!
* A behind-the-scenes look at the creation of Bravely Default.