Júlia Sardà is best known as the illustrator for such books as The Hotel Balzaar by Kate DiCamillo, Moving the Millers' Minnie Moore Mine Mansion by Dave Eggers, The Treasures of Barracuda by Llanos Campos, Rose Campion and the Stolen Secret by Lyn Gardner, Mary Who Wrote Frankenstein by Linda Bailey, an illustrated gift edition of Mary Poppins, and Sweep by Louise Greig. The Witch in the Tower is set in the same world as her author-illustrator debut, The Queen in the Cave. She lives in Barcelona.