In 2013, Knox published "Mortal Fire", a young adult novel described by Paula Green as "a modern fairy story without fairies, full of breathtaking magic and visual detail", and "Wake", a horror novel for adults. "The Guardian" said in its review: "Knox keeps the monster off stage and examines the psychological consequences of its depredations on the survivors, subverting the norms of the horror genre and thus making the ambiguous finale all the more startling." The publication of both books in the same year caused some confusion, with New Zealand bookstore Whitcoulls inadvertently shelving "Wake" in the children's section and listing it as a "great gift for kids".