Nor do dictionaries shed much light on the matter. According to the Oxford English, an autobiography is "the writing of one's own history; the story of one's life written by himself," while a memoir is "a person's written account of incidents in his own life, the persons whom he has known, and the transactions or movements in which he has been concerned; an autobiographical record."
For me the difference is mainly one of audience and intention. Autobiographies are penned by the famous or infamous for an audience interested to hear their life stories; memoirs are written by the relatively obscure or by those who have merely brushed up against fame, with the intent of treating a specific broader theme or issue with which the author is intimately and by personal experience acquainted, but which is not purely personal.
Which is a long way of saying that a memoir is about something other than the life of its author. If you're Dolly Parton or Bono, you write your autobiography. If you're somebody like me, and feel so inclined, you write a memoir.
Memoirist Nora Gallagher sums up more succinctly still the secret to writing good memoirs. "It's not about you." When, in Autobiography of a Face, Lucy Grealy writes about losing half her jaw to cancer and the ramifications of being permanently disfigured, she's not merely talking of her own personal ordeal; she speaks to any and all of us who've ever been self-conscious of our looks or suffered rejection or endured physical torment and pain, or who've been torn between who we are, and what we wish to be—in her case, someone with a whole face and not one torn in two by cancer. Singularly horrible though her experience may be, still, there's much in it that we can all relate to. And it's the relatable part that is her book's true and worthy subject.
The first page here is from the memoir of a pilot. The most famous example of the genre (if it can be called that) is Wind, Sand, and Stars, by Saint-Exupery. Here is how Saint-Exupery opens his memoir:
In 1926 I was enrolled as a student airline pilot by the Lactécoère Company, the predecessors of Aéropostale (now Air France) in the operation of the line between Toulouse, in southwestern France, and Dakar, in French West Africa. I was learning the craft, undergoing an apprenticeship served by all young pilots before they were allowed to carry the mails. We took ships up on trial spins, made meek little hops between Toulouse and Perpignan, and had dreary lessons in meteorology in the freezing hangar. We lived in fear of the mountains of Spain, over which we had yet to fly, and in awe of our elders.Note how quickly the focus here switches from the narrator to his fellow pilots in the aggregate ("It's not about you."). From this opening paragraph on Saint-Exupery's book will of course be about him, but it will mostly be about pilots, flying, the mail service, the poetry of land as seen from the air . . .
By contrast, judging by its opening paragraph, the memoir being considered here, though quite well-written, is strictly personal. And that's the problem. The author has put his best foot forward, so he thinks, and its an autobiographical foot. It begs the question: what's in it for the reader? Why should a perfect stranger care that so-and-so was offered a job at TWA—a company that doesn't even exist anymore? How relatable is that?
From there the narrator treats us to the intricacies of the probationary period —but this, too, is treated not historically, or even nostalgically (by way of saying how things were different back then), but personally: this is what happened in my case, to me, at my airline. Fascinating? Yes, assuming that the reader has a personal reason to be fascinated—if she happens to have known the author, for instance. Otherwise, in spite of the good prose, I'm afraid this won't fly.
But solutions may be at hand. One might be to follow Saint-Exupery's example and switch the focus to the aggregate over the individual, to make this a memoir about flying for the airlines back then—not one man's story, but the story of an industry in its relatively glamorous days.