Howl's Moving Castlle by Dianne Wythh Jones.

Adapted into a film by Japanese filming studio Studio Ghibli, Howl's Moving Castle was a global hit when it was published. 

Howl's moving castle has a magic door that opens onto four different locations: the hills above Market Chipping, where the castle appears to be running around; the seaside town of Porthaven, where the castle is actually located; the royal capital of Kingsbury; and Howl's original home in Wales.

Sophie is 18 years old, the eldest of the Hatter sisters, with red-gold hair and baby blue eyes. Her loneliness changes when she meets wizard Howl. The Witch Of the Waste takes issue with their budding relationship and casts a curse on Sophie, turning her into a 90-year-old woman. Howl is depressed because he thinks Sophie has left him.  He is also cursed by the witch of the waste too because he worked with Calicfer the flames. Howl makes a bargain with Calcifer. Calcifer gains Howl's heart but is bound to serve Howl (heating water, moving the castle, etc). The problem with the deal is it strips Calcifer of his freedom and leaves Howl heartless (in the emotional sense as well as physically).

This book is amazing, and it's like a romance and a comedy and an adventure and a thriller and a horror...

You know what, read it yourself!

Enjoy the book!

Regards,
Emmi x