According to William Morris, one of the major thinkers, and designers, of the Aesthetic Movement, you should "have nothing in your house that you do not know to be useful, or believe to be beautiful". This injunction has always puzzled me, because of that "or": there seems to be some choice involved between utility and beauty. Presumably a knife is one thing, so useful for cutting lamb chops, and gorgeous cushion covers (from Morris & Co) quite another. But a cushion cover is also useful, isn't it? So is a well-designed chair or fabulous table, a curtain or bedspread? Morris designed all of them to be both beautiful and useful.

The stronger claim – have nothing in your house that isn't both beautiful and useful – is more compelling, and is indeed the mantra of most designers of the homeliest artefacts. You want a knife? Why not buy some Georgian silver? Or, if you can stump up for it, one designed by Charles Rennie Mackintosh? Surely a choice of such an object is not based on its utility – all knives will cut a lamb chop – but additionally on how attractive one finds it?

It is harder to make the inverse claim: that objects of beauty should be chosen, too, for their usefulness. You might make such a case, even, for paintings: being surrounded by the beautiful works of art is calming and delightful to the soul, and such an aesthetically-enhanced inner organ may well make us perform better in our daily lives.

But I am not much interested in pursuing this, because what I am really interested in here is bookshops. A recent post on this website by Sarah Crown enthusiastically described the "most beautiful" bookshops she has encountered. Readers were invited to add further examples, and pictures were posted of book-lined rooms replete with comfy sofas covered in chintz, tables with pretty little lamps and a vase of tulips, Persian carpets – all the cosiness of a cottagey sitting room redolent of brewing tea and baking scones. Flyers announcing forthcoming poetry readings behind the desk. Mozart playing, soothingly. Nothing that isn't enhancing to the spirit.

What a delight to enter such a place, pick a book off a shelf, plump up a cushion, accept the offered lapsang souchong (lemon only, ta!) and settle down for a read!

Such a shop is intended to offer an experience so thoroughgoing it might be described as organic, in which the environment is as booky as the books, and one is comprehensively immersed in the pleasures of being and reading.

Sounds great, but it doesn't work for me, as it so obviously does for Sarah and her many enthusiastic commenters. This may be because I am a book dealer, and my demands on a bookshop are often specialised, but I am also an avid reader, and I buy a hell of a lot of books. And the kind of (both beautiful and useful) bookshop that has been described is frequently, in my experience, exactly the sort of place that I am disappointed, and frequently exasperated, by. (Though I find more of these in America, I can think of a good few examples in the UK as well.)

The reason for my unease is that what is so lovingly created in such settings is not a bookshop, but an idea of a bookshop. It is a sentimental idea, a kind of pastoral often untouched by serious commercial consideration. The kind of bookshop you might find in a Beatrix Potter book, with browsing rabbits. Why bother choosing a great stock when you can provide a great environment? "This is such a lovely shop," customers (not!) will swoon over their cup of tea, "I just adore it here!" But the purpose of a bookshop is not to make its patrons sigh with pleasure, but to make them buy books. And I have seen scant evidence that, as a marketing strategy, the beautiful bookshop works very well as a selling venue. Some may succeed in spite of their beauty – through a great location or an excellent stock – but few because of it.

What is it you want when you go book hunting? I want to buy books. I want a well-chosen, wide-ranging and well-priced stock that makes me start making a pile of potential purchases. I do not need a sofa, can happily dispense with the Mozart, and am not likely to engage in much conversation. They get in the way.

I am not averse to excellent shops in which the proprietor also attempts to make the environment welcoming and attractive, but it is largely my experience that the more beautiful the shop, the less tempting the books.

One of my favourite bookshops, recently closed due to the death of the proprietor Peter Howard, was Serendipity Books in Berkeley, which was exceedingly useful, and pretty comprehensively unbeautiful. Peter was an obsessionally dedicated and knowledgeable bookman across a remarkable variety of fields. He was generous and warm-hearted on his day, but he didn't have many of them. Mostly he ranged from grumpy to curmudgeonly, and was uncommonly fond of making his customers feel ignorant, and then guiding them towards the light. His shop was strewn with hundreds of thousands of books, arranged in ways that were never obvious, so that – this was the point – you had to do some of the work yourself. And, if you did, it was quite impossible to go into Serendipity and not emerge with a serious bunch of books.

The shop had a quirky sort of charm in that old Beatnik fashion, and on one of Peter's good days you might get a coffee, but his purpose in being there was either to lecture you or to sell you books. Preferably both. What you paid for them often bore no relation to the pencilled price inside the book. I remember once buying a book marked at $400, which he examined carefully and then charged me $93.50 for. I had learned by then neither to haggle, nor to inquire how the final figure was arrived at. It was an experience just going to Serendipity: unpredictable, frequently infuriating, anecdote-generating. It wasn't cosy.

But there are plenty of examples of what I think of as unostentatiously pretty bookshops, with attractive and well-kept premises that provide a backdrop for an excellent selection of books. I am thinking, say, of Daunts in Marylebone, or Maggs Brothers in Berkeley Square. Places that are a pleasure to be in, but where the focus is on the shelves not the stage set.

Maybe William Morris was thinking about bookshops? Here there often is a choice between the beautiful and the useful, and give me the latter any day. I can find plenty of delightfully cosy rooms elsewhere, but it's hard to find great places to buy books.