Quirky and improbable, just like real life This is first and foremost a writer's story, and I thoroughly enjoyed it, storyline, screenplay, and acting. Author Alan Bennett (played with deftness, subtlety, and, one can't help thinking, great honesty, by Alex Jennings) found an unconventional and quirky approach to telling a true story as it unfolded - from the unique perspective of a playwright, for whom everything is a potential plot element and everyone a potential character. This is not a case of the playwright deliberately inserting himself into the story - he is an essential element of it, and the audience is not to forget it. Along the way of unfolding the history, he not only presents the observed facts, but lets the viewer in on how those facts appeared to him, and how they affected him as victim and as playwright. He unabashedly (and increasingly) plays teaching games with the audience, giving them opportunities to understand not only what is driving the action, but also *how* he is helping them follow what is happening; you can easily imagine the author says "look, audience - do you see what is happening here?"
According to what I can glean from various sources, the "mostly true" story is very largely true (the few additions are useful devices in order to illuminate some of the unknowns), but Bennett did not really know just how much of it was during much of the plot. His place in the unfolding mystery of "Miss Shepherd" is as central to the movie as the mystery itself.
Maggie Smith plays a complex, somewhat neurotic, almost pathologically secretive character, whom the writer - as a writer - can't help finding as fascinating a study as she is unpleasant and aggravating to deal with. It's tempting to lump this character in with other "difficult" women she has played in recent years, but it most emphatically stands on its own. She is not cute, or wise, or endearing, but pitiable and very real. A couple of added events in her story are improbable (of course much of the literal truth is as well), and apparently supplied or altered for dramatic effect, but to good purpose: they are shorthand mechanisms to help convey essential facts that the characters could not express more directly. The truth - the playwright's truth, that is - prevails.