Late author Diana Wynne's final book that was left incomplete is being completed by her sister Ursula Jones and is slated to be published next year.

Author Diana Wynne was writing a book when she passed away. The book titled "The Islands of Chaldea" is now being completed by her sister Ursula Jones and will be published next year.

Wynne was working on the story when she was diagnosed with cancer and soon became too ill to continue, reveals Jones. Wynne passed away battling the disease 2011, leaving behind some of the best regarded novels in children's fantasy to her credit like the "Chrestomanci" series and "Howl's Moving Castle."

"Everyone in the family knew Diana was writing her book, but no one really knew how much she had left to write. She got so ill she had to stop and most of us felt 'oh that's that'. And then her husband, I think it was, suggested someone might complete it," said Jones in a report published by The Guardian.

Jones said that it was her sister's agent who suggested she finish the book before anyone else attempted to, as they both belonged to the same family. People, who have read what's finished of the story, haven't been able to guess the part from which she took over. She calls it "a good endorsement."

"Diana was very much my eldest sister, and I was very much aware of a fury from her, either that I was doing it, or that I was not doing it fast enough. I had awful nightmares about it. It was curiously traumatic," she said. "I was conscious of her looking over my shoulder in many different ways. To start with, there was this disturbing feeling of fury. Then once I'd got under way there was almost a moment of rather grumpy 'oh all right then'. I'm not a believer in any of this sort of thing but I tell you it was palpable, and quite uncanny.

The new novel talks about a group of four warring islands, where a king's son is held for ransom behind a magical force field which a young girl and her bossy witch aunt set out to fight.