Somewhere or other Barbara Pym remarks that the most soothing bedside reading is a cookery book. There is nothing nicer than a paperback of clever, surprising recipes to fill you with happy thoughts of future possibilities, mostly involving bacon.

Perhaps because they act so calmingly on the psyche, there is no literature more unchanging in its appeal than the literature of food. You can read Eliza Acton, or Apicius, and feel that, to some degree, nothing has changed, and people still eat many of the same things that they did a hundred or a thousand years ago. "Egg", after all, is one of the oldest of all English words, and I don't suppose that many new ways have been evolved to eat them in the last millennium.

But, strangely enough, cookery books also draw on aspiration, fantasy and the limitations of their time. They are, paradoxically, also the form of literature which witnesses changes in fashion most dramatically. If you pick up a commercially successful cookbook of 50, 30 or even 20 years ago, it is quite startling how our tastes have altered.

For 20 years or so, between the late 1970s and the mid 1990s, one author reigned supreme, and her name was Delia. Every student was sent off to university with her black-bound cookbooks; either the three separate volumes, or, a little later, the one-volume reduction. That last one had a photograph of Delia herself holding an egg, one eyebrow raised. In my student house, we sat around for hours discussing the slightly alarming erotic appeal of the image, without ever coming to any conclusion. The great attraction of Delia Smith's cookbooks, as everyone always says, is that the recipes work, infallibly. Her no-nonsense approach succeeded in taking our innocent hands and leading us, with surprising success, into the kitchen. Looking back at it and her subsequent books, you can see a solid basis of English, Eliza-Acton cooking style. (I roasted a goose from Delia recently with notable success).

But overlaying this is evidence of the rise of package holidays, of the appeal of the exotic. Delia put pesto in places no Genoan had ever contemplated, and mixed and matched culinary cultures with gay abandon. I remember once at a dinner party being served, in succession, mushroom risotto, Thai red chicken curry and bread-and-butter pudding. You can't help but feel that Delia's globe-trotting forays had encouraged that sort of recklessness.

All the same, the old girl introduced us to all sorts of ideas. I had a long period, in the late 1980s, of cooking mostly from Marcella Hazan's wonderful Italian books. But I first heard of ragu and gnocchi from Delia. Subsequently, I've gone through a phase of blood, guts and Fergus Henderson. My current obsession is Simon Hopkinson's superb, post-ironic, classically elegant rediscovery of the postwar plate, The Prawn Cocktail Years – I've ventured Duck a l'Orange with great success and am working up to Chicken Maryland. It must be said that almost all subsequent enthusiasms spring from a little seed of keenness, planted in the late 1970s by Delia.

If you were posh or socially pretentious, no doubt you learnt from Elizabeth David. I guess that was what Barbara Pym was talking about – her books are terribly comforting last thing at night. But most of us learnt how to cook from the wonderful Marguerite Patten and then from Delia Smith. If they contain aspirational elements, they are the same aspirational elements which have shaped their readers' lives. There are no absurd ingredients, and nothing which is not meant to be cooked.

So Delia's new cookbook, designed for cheats or those with little time, is going to fly off the shelves, and probably deservedly so. The idea of the book is that everyone has time to cook, even if it means depending on ready-prepared items. I don't believe that Delia takes money in return for recommending products; I think she genuinely finds products which she likes, and passes the tip on. I'm honestly surprised to see her recommending a brand of instant mashed potato, something I always believed to be the food of the devil. But, being Delia, she gets the benefit of the doubt.

Whether this really is a problem which can be solved by pre-prepared, dried and tinned goods, I doubt. Cooking needn't take much time or effort at all. To fry calves' liver with sage and butter takes three minutes, if that; roasting a joint of meat requires 30 seconds' worth of preparation. The problem, really, is a larger one than food, the way that people in the past two decades have shifted many elements of their daily life into the realm of spectacle and entertainment. Even Delia can't do much about that. But she's in a good position to make an effort.