Her agent Dan Strone at Trident Media Group said today that she died in a fall from her riverside apartment in London on Sunday. He didn't give any more details.
She was known for her books about David Bowie, John F. Kennedy Jr., Arnold Schwarzenegger, Grace Kelly and other major figures.
British media commentator Roy Greenslade said on his blog that Leigh had a popular touch.
"She moved on from sex manuals to write a series of celebrity biographies, most of which antagonized her subjects.
But they were always scrupulously researched and full of interesting psychological insights," he said of Leigh.