Well, I did get a bio of AC, and although I was disappointed with it (I won’t name it but it read more like an extended magazine article, with chapters often of two or even one and a half pages in length) but it did tell me much more about Agatha’s famous, mysterious eleven days.
And the truth seems to be that they aren’t very mysterious! If this book is anything to go by, she was seriously depressed after her mother’s death and on finding that her husband was having an affair and likely to leave her, and had hinted at suicide to friends. Thus she set off in her car and tried to drive it into a quarry. Being a woman driver she hit a tree instead, banged her head and lost her memory. At the hotel where she stayed, rather than staying enigmatically in the background she joined in with the social activities and even drew attention to her likeness to the pictures of the missing authoress in the papers. She seems to have been genuinely convinced that she was someone else altogether, and it also seems clear that she was suffering from concussion and some sort of post-traumatic stress disorder.
And, contrary to the impression often given in accounts of this period, she wasn’t at all coy about it and even gave newspaper interviews.
She might have called it The Mystery that Never Was!