One of my favorite books of all time is Howl's Moving Castle by Dianne Wynne Jones. It is magical realism at its finest.
Sophie, the eldest of three girls, gets on a witch's bad side. The Witch of the Waste (great name for a witch) puts Sophie under a spell, transforming her into an old woman. Her only chance in breaking the spell lies with a grumpy wizard named Howl. Sophie manages to get a job cleaning Howl's house in an effort to convince him to break the spell. Once she's in the house, she discovers there's more to Howl, his castle, and herself.
It's such a magical, fun book. About a castle that moves. What more could you want? You can go anywhere without leaving your home. It's an introverts dream.
While I adore Sophie and, eventually, Howl, the fire demon is my favorite. Calcipher lives in Howl's castle. He is there under contract with the wizard and can't leave the hearth without Howl's help. So, he's there, but against his will. He strikes a bargain with Sophie, promising to use his magic to break the spell the witch put on her so long as she helps him get out of his agreement with Howl.
Howl is heartless, he is hateful, he is mean. By the end of book, we learn more about Howl and how he earned is reputation.
I first read Howl's Moving Castle about ten years ago and it's stuck with me. Magical realism is not my normal thing, but it fits here. And summer seems like the perfect season to read about witches and wizards, spells, old ladies who are actually quite young, and, of course, fire demons.
Howl's Moving Castle is the first in a series, but you can read it as a stand alone. Read it and then watch the movie. Because the castle is so rad.