Charles Scribner's Sons, New York, 1966. Hardcover. First Edition (Scribner's Sons-: 'A--8.66' on the copyright page). This was Ann Quin's second novel and first novel published in the United States. The Scribner's Sons first edition is quite rare. I've only seen one other for sale. 

From the Paris Review: 'Three is the second of the four brilliant and enigma-ridden novels that Ann Quin published before drowning off the coast of Brighton in 1973 at the age of thirty-seven. The mysterious character S--the absent protagonist or antiheroine hypotenuse of this love-triangle tale--dies in similar fashion, or perhaps she's stabbed to death by a gang of nameless, faceless men before her body washes up onshore, or perhaps the stabbed dead body that washes up onshore is someone else. It’s difficult to tell. And the telling is difficult, too. And I would submit that it's precisely these difficulties that make this gory story normal.'

From a source on the Internet: 'Three opens with the death of a young woman, identified only as S, possibly a suicide. Following her death, Ruth and Leonard-- a middle-aged British couple whose marriage has devolved into pithy and bitter conversations-- review the time S spent at their summer house. 

In a lyrical prose style likened to that of such diverse writers as Virginia Woolf and William Burroughs, Ann Quin presents the enigmatic intricacies of the relationship between these three people by blending the conversations and flashbacks of Ruth and Leonard with the diary, audiotapes and movies S left behind. 

A combination of laconic dialogue and poetic impressions, Three is an incisive exploration of the emotional and sexual undercurrents of British middle-class life.'