At 17, Mildred married Bert Pierce and quickly had two daughters, Veda and Ray. They lived well off the sale of new housing subdivisions until the Depression hit, leaving Bert (who'd never really had a job) essentially unable to cope with his uselessness. Mildred, who'd been making a few odd dollars baking cakes and pies, threw him out, looked for work, and eventually swallowed her pride and became a waitress in a downtown diner. With the help Bert's former business partner, she opens a restaurant, and eventually expands her business to three restaurants with different atmospheres and a commercial baking business supplying pies to other establishments. Then, because of her poor choice in men and inexplicable devotion to her monstrous daughter Veda, loses it all.
I know it sounds like a fairly routine book, but what saves Mildred Pierce is the characters. Bert's a decent guy, just not quite up to the challenges of surviving the Depression, and he stands by Mildred, proud of her success and there for her when she fails. They don't really want to divorce, and maybe Mildred would have been better of staying with him. But she doesn't - as her business takes off, she begins an affair with Monty Bergeron, a wealthy man who sleeps with her and scorns her and take her money when he his family fortune disappears but bonds instead with Mildred's haughty teenage daughter Veda. There's a subtext there that 'polite' novels would have ignored in 1941, but I suspect that pulp readers saw what I saw in Monty's comments about Veda's emerging bust, or in the closeness between the two. Mildred, however, doesn't see anything inappropriate in the relationship between her daughter and her lover, and also doesn't see that her beautiful and musically talented daughter constantly manipulates her. It's Mildred's devotion to Veda's musical career that leads to the loss of her business, and eventually to her loss of Veda.
The other thing I noticed while reading Mildred Pierce was how foreign the novel's setting appeared, even though it takes place in the decade before my parents were born. Not everyone has a telephone, radio was new, and a blood transfusion from a professional donor with no testing or typing is seen as a potential cure for a bacterial infection. Like Knots and Crosses, Mildred Pierce is set in the close enough past to be recognizable, but far enough away to be almost an entirely different world.