E. Aster Bunnymund and the Warrior Eggs, by William Joyce, Atheneum Book, 2012.
On very rare occasions, I watch a movie before I read the books. In my defense, I didn't know about the books when I bought the movie The Rise of the Guardians for my son. And, after the movie, I wanted to learn so much more about the characters.
I am LOVING this series. E. Aster Bunnymund is rather different in the book than he is in the movie, but, in my mind, he still talks like Hugh Jackman.