Short answers, pulled from the story.
Diana Wynne Jones was a British novelist, poet, academic, literary critic, and short story writer who lived from the 16th of August 1934 to the 26th of March 2011. She principally wrote fantasy and speculative fiction for children and young adults, including the Chrestomanci series, the Dalemark series, the Moving Castle novels, and the nonfiction guide The Tough Guide to Fantasyland.
Howl's Moving Castle is a 1986 fantasy novel by Diana Wynne Jones, inspired by a boy at a school she visited who asked her to write a book called The Moving Castle. It was first published in the United States by Greenwillow and was a runner-up for the Boston Globe-Horn Book Award. Hayao Miyazaki adapted it into a Japanese animated film in 2004, which was nominated for the Academy Award for Best Animated Feature.
Diana Wynne Jones won the 1978 Guardian Children's Fiction Prize for Charmed Life, the Mythopoeic Fantasy Award twice (in 1996 for The Crown of Dalemark and in 1999 for Dark Lord of Derkholm), the British Fantasy Society's Karl Edward Wagner Award in 1999, and the World Fantasy Award for Life Achievement in 2007. She received an honorary doctorate from the University of Bristol in July 2006.
Philip Pullman, Terry Pratchett, Penelope Lively, Robin McKinley, Dina Rabinovitch, Megan Whalen Turner, J. K. Rowling, and Neil Gaiman all cited Jones as an inspiration. Gaiman described her as "quite simply the best writer for children of her generation" and had dedicated his 1991 comic mini-series The Books of Magic to four witches, Jones among them.
Jones's first book was Changeover, a novel for adults published by Macmillan in 1970. Set in a fictional African colony undergoing decolonisation, it is a farce in which a memo about how to mark the changeover ceremonially is misread as referring to a terrorist named Mark Changeover.
Diana Wynne Jones died on the 26th of March 2011 from lung cancer, having been diagnosed in the early summer of 2009. Her unfinished novel The Islands of Chaldea was completed by her sister Ursula Jones and published in 2014. The Mythopoeic Society nominated it for its Fantasy Award for Children's Literature in 2015.