I've noticed that many of the questions people have about memoir are tied to authors' fidelity to lived experience. Has the author presented a very subjective account of events? Perhaps, even invented material? Is the the story a faithful one?
One response to these questions is to say that all narratives are inventions of a kind. As soon as a story is shaped into artistic experience, it becomes a textual representation rather than reality. But that doesn't quite do justice to the question, which is really about the nature of that representation rather a naive wish for absolute accuracy.
In the subject that I teach, I approach the topic from the point of view of the creative techniques that are being used, and discuss these questions in terms of a spectrum of literary devices rather than a division of absolutes, one that would have fictive work on one side, truthful writing on the other. I have to admit that, in my own nonfiction, I do aim for a high level of factual accuracy, as high as I can manage. But I find that this spectrum-based approach to creative techniques in nonfiction allows for a less black-and-white analysis of memoir and it impact, and one that ties creative techniques to the narrative personality of the writer.
Didion's book performs, at a formal level, the very content that she's describing: the work circles and sometimes avoids a central death scene in something like the way Didion both faces and avoids the reality of her husband's death. Garner's book, which is a true crime novel, adopts a number of features of fictional crime writing, especially in her use of characterisation and what's sometimes referred to as "police procedural". Boo's work, also about a criminal case (although very much in terms of the setting and lead-up to it) features the novelistic use of point of view and internal, highly subjective characterisation. Eggers's study of his relationship with his brother after the death of their parents mixes many literary forms, I think partly as a way of resisting sentimentality and some of the other conventions of the genre known as bildungsroman, or, in this case, künstlerroman (a novel of the early life of an artist). Winterson, meanwhile, has spoken about the non-linear nature of her novel, one that adopts both a very realistic tone and also moments that might be better described as mythical and fantastic.
In interviews that I've conducted with authors of memoir, I've noticed that they, too, imprint their life stories with their personalities as writers - the books express their way of representation, as much as what they want to say. Lloyd Jones's A History of Silence is an intricately-structured account of secrets in his family: the structure is his way of representing (in the book's form) the intricacy of family history.
Jessie Cole's Staying is notable for its use of a lyrical voice that we might associate with fiction. Meanwhile, when I spoke to Annie Proulx about her memoir Bird Cloud, I was struck by the way in which she constructed the narrative as a series of stories that surround the property at the centre of the book. And, quite recently, I interviewed debut novelist Trent Dalton about his fictional but heavily autobiographical work Boys Swallows Universe. It mines his childhood experiences of growing up in suburban Brisbane while using an intensely subjective voice of fictional first person narration, which tends to be more immediate and open than first person as it's used in nonfiction.
What each of these books suggests to me is that, in the case of memoir and autobiographical fiction, we can read both the content and the form as different aspects of autobiography. Each expresses the author's personality: how they tell a story as well as the story they have to tell.