It was always the fragile balance of opposing forces that made Diane Keaton’s face so remarkable — those tilted melancholy eyes above that frequent and infectious smile. She seemed in a perpetual state of emotional contradiction, which is one of the things that made her such a perfect match, at least on film, for Woody Allen, who as history’s most hopeful pessimist is a master juggler himself.

So it’s not surprising that Keaton’s memoir, Then Again is also an elusive sort of work, part autobiography, part daughterly paean, part love letter to her own children, a book in which portions of her mother’s journals and details of her parents’ travails in old age far outnumber the on-set anecdotes and glamour shots.

Keaton writes not so much in chapters, though there are chapters, but in pieces, some rushed and breathless and vague, others almost journalistic in their determination to get the facts right, all of them evocative of her famously elliptical cadence and non sequitur manner, which is just as effective and irritating here as it is on screen. It would seem that at some point an adult woman of certain experience should be able to speak in simple declarative, unapologetic sentences and write a simple, straightforward book about herself.

But truth, like beauty, comes in many packages, and if Then Again is not a beautiful book, it seems like a truthful one, revealing a woman still plagued by insecurities, though not enough to keep her from being an actor or writing a memoir, and weighted down with regrets, though not so many to keep her from adopting two children at an age when most women are surveying an empty nest.

The big reveal of Then Again (besides Keaton’s claim that Allen had a beautiful body) is that for many years Keaton was bulimic, excusing herself from real life to soothe herself with prodigious amounts of food (lovingly cataloged in detail only a true addict could muster after all these years) of which she then rid herself. The confession is not particularly surprising — Actress has issue with weight/food! Details at 11! — but the aplomb with which she handles it most certainly is. She discusses it in the middle of the book, refuses to offer armchair diagnosis or blame, and then she moves on. She doesn’t use it as a symbol for her life or spine for her narrative; she doesn’t use anything as a spine for her narrative.

In fact, while reading Then Again one would do well to remember Keaton’s love of photography — she has curated several collections and learned, from her mother, the art of collage. Then Again often feels like a collage, or a collection, of moments and thoughts and images, that stay with you longer than you suppose they might because they are so often contradictory and unsettling.

Although by any standard save Meryl Streep, Keaton is a successful actor, she spends very little of Then Again discussing her profession. The men she met through her profession, yes, but very little of her passion for acting or the craft of making a movie. She does say she hated playing Louise Bryant in Reds because “there was nothing charming about her will to be recognized as an artist in her own right.”

Keaton may have come of age in the ‘60s — her breakout role was in Hair, though she kept her clothes on — but she seems to have a very old-fashioned view of romance. When discussing the three big loves of her life — Allen, Warren Beatty and Al Pacino, none of whom, she says, loved her enough to marry her — she inevitably and repeatedly defers to their brilliance. Allen is a genius who remains “borderline repulsed by the grotesque nature of my affection.” Her performance in Reds was “more like a reaction to Warren — that’s what it was: a response to the effect of Warren Beatty” and Pacino made her “think about the difference between being an artist and being artistic. I knew where I stood. I was artistic.” Even Jack Nicholson, her costar in Something’s Gotta Give, was so magnificently distracting that during a kissing scene she kept flubbing her lines.

All of which can be a little wearing except, you know, here she still inarguably is, Diane Keaton, still making movies, raising her kids, giving interviews, writing this book that fits no construct or style but her own. Then Again reads like the diary of an ordinary woman who suddenly became a movie star, who doesn’t quite believe any of it happened, but it did, and even though she isn’t quite sure any of it makes sense anyway, she has just enough chutzpah to believe that you might find it interesting enough to read.

And you might. In the end, I did.