She wrote more than 80 books.
http://www.guardian.co.uk/books/2009/nov/12/louise-cooper-obituary
Excerpt:
Born Louise Antell in Barnet, Hertfordshire, she had a happy childhood
in which lessons were often neglected in favour of clandestine story-
writing. Her determination to become a writer eventually persuaded her
parents to allow her to abandon her education at the age of 15, and
she left St Albans high school for girls to pursue this dream.
The gamble more than paid off. In 1972 Louise moved to London to work
as a blurb-writer for a publisher and
continued to write in her spare time. Her first novel, The Book of
Paradox (1973), was followed in 1977 by Lord of No Time, which was
later expanded to become the Time Master trilogy (1986), an epic adult
fantasy sequence, for which she went on to write both sequel and
prequel trilogies. It secured her a huge fanbase and a global
reputation as a master of her craft.
http://news.google.com/news/search?aq=f&pz=1&cf=all&ned=us&hl=en&q=%22louise+cooper%22
(more obits, including ones in Italian, French, Spanish and German)
Lenona.