I think I've got it! Several of my previous posts have questioned memoirs as a literary genre but I now realise that adding a memoir to a book title is the publisher's construct. Authors writing about important parts of their life are not confined by genres - they are telling their own story. Annie Proulx in her latest book Bird Cloud is telling the story of her dream house and woven into that story are many strands of history, genealogy, zoology, geology, ecology, philosophy and literature, in wonderful crystal clear writing. Penelope Lively in A House unlocked described her childhood house through its many generations of residents discussing the relevant social conditions of the day and the psychology of families and relationships.
These books are more than memoirs, wider than biography and deserve not to be pigeon-holed into any particular genre. They do deserve wide reading!