Title: The Frog Princess
Author: E.D. Baker
This is a great book!
It's about Princess Emeralda (Emma for short). One day, she goes to the swamp and meets a frog named Eadric who is an enchanted prince. Emma kisses him, thinking the kiss would turn Eadric back into a prince. But instead, Emma turns into a frog as well. Now they must go on an adventure to find a way to reverse the spell.
I give this book
(If you were wondering, yes, Disney's "The Princess and the Frog" was based off this book).