It’s quite hard to give, in a short review, a full flavour of Ysenda Maxtone Graham’s book about women’s working lives from 1950 onwards; to be frank, I can’t remember the last time I read something so potty – in good ways, and in bad. But for starters, let us begin with Penny Eyles, who in 1950, at the age of 22, found herself working briefly at a place called the De La Warr Laboratories, near Oxford. According to Eyles, whose job was to type letters to the aristos who swore by the treatments it offered, the “laboratory” comprised lots of black boxes, each labelled with the name of the patient to whom it belonged. Inside the boxes were samples of the patient’s blood and hair, various knobs and dials, and a strip of rubber. Every week, a medium called Mrs Boulder would arrive to “treat” the patients by rubbing the, er, rubber strip, at which point the dials would apparently begin to move.

You have to ask: where on earth does Maxtone Graham find them? My sense is that she doesn’t cast her net particularly widely. Admittedly, in Jobs for the Girls, the third in her trilogy about “lost worlds” of the recent past, there are a few non-posh people: one of her interviewees worked at a Tampax factory in Havant; another was employed at a Bradford mill. But the vast majority have names such as Phoebe Fortescue and Bumble Ogilvy-Wedderburn, and the trouble with this is that the Fortescues and Ogilvy-Wedderburns of this world tend to have things a bit easier than the rest of us; De La Warr Laboratories aside, they can afford to be eccentric (and to flit, as Penny did, when they get a better offer, which they always do). However much we may sympathise with some of the struggles they describe in Jobs for the Girls – their daddies were dastardly not to want to educate them properly, and yes, it was a pity their schoolmistresses thought their best course was to “marry into” a grouse moor – when they confess to how bored they felt at Christie’s, or to how disappointing it was that life at BOAC was not at all as it appeared in a book they read at boarding school called Anna the Air Hostess, you feel irritated even as you laugh.

The comedy that served Maxtone Graham so well when she was writing about holidays in the sublime and bestselling British Summer Time Begins is less effective here, mainly because, unlike Thermos flasks and holiday camps, work is terrifyingly crucial for all women but a rarefied few, and was so even in the period covered by her book (1950 until the early 1990s). On the plus side, the period detail is glorious: think boiled beetroot in white sauce for supper (a dish served by a Miss Ling to trainee secretary lodgers at her Cambridge boarding house), post room crushes and acoustic modems made of mahogany and green baize. How extraordinary to read of finishing schools where girls from rich families learned to cook, supported by legions of maids who put out all their ingredients and did the washing up afterwards (said ingredients included, at one Scottish establishment, the heads of sheep, from which soup was to be made; students were instructed first to remove the grass from the animal’s teeth). How baffling to learn that trainee air hostesses – a “little” job that was popular pre-marriage on account of the glamorous layovers – were instructed in all seriousness that if their pilot came knocking on their hotel door asking for toothpaste, they should not open it. Rather, they should squeeze the toothpaste “through the keyhole”.

But on the downside, Maxtone Graham’s determination to play the glad game, and to make assumptions based on her own experiences, brings her to some preposterous positions. No, working-class girls who did piecework in clothing factories and upper-middle-class girls who made darling little jackets at finishing school really were not in similar situations; it’s insane to suggest, as Maxtone Graham does in this instance, that an inadequate education “could be a great leveller” (an inadequate education affects the less well off disproportionately). It’s also a pity – sorry to have to pull on my dungarees here – that the book is shot through with internalised sexism, including on the part of its author, who asserts that men often made better bosses than women, “who went around poisoning the working environment with their subtle jealousies, favouritism and moody silences” (ugh).

To be fair, there are some horror stories here: the passes, the belittling, the throwing of ink wells at secretaries’ heads. On the other hand, it was discombobulating to read her determinedly optimistic speculations about “bottom pinching” – such behaviour had died out by the 1980s, at least in the office of Harper’s & Queen, where she worked – in the week that we learned that one in three female NHS surgeons in England have been sexually assaulted by male colleagues in the past five years. In the end, I must admit, I hardly knew what to think about this book. I love Maxtone Graham’s curiosity, wit and nose for eccentricity; I’m obsessed with the De La Warr Laboratories, and long to put them in a novel. But ultimately, Jobs for the Girls is just too horribly partial for me to love it as I did British Summer Time Begins.

• Jobs for the Girls: How We Set Out to Work in the Typewriter Age by Ysenda Maxtone Graham is published by Abacus (£22). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply