The Bolter

The story of the wild, beautiful, fearless Idina Sackville, descendant of one of England's oldest families, who went off to Kenya in search of adventure and became known as the high priestess of the scandalous "Happy Valley Set"

by Frances Osborne

New York: Knopf, 2009. She inspired the character of 'The Bolter' in Nancy Mitford's Pursuit of Love, and was Vita Sackville-West's cousin. I haven't read this yet, but it does look good!  Hardcover with dust jacket in very good condition. (note: the jacket is designed to look a bit antique-y, so any wear you perceive in the book photograph is actually part of the book design.)