World Book Day is upon us, and primary school classrooms across the country are filled with overexcited, undersized BFGs, Mary Poppinses and Gruffalos. Meanwhile, parents will be arriving at work frazzled and smeared with facepaint. Because as we all know, despite the very best efforts of its organisers, World Book Day isn’t principally about reading – it’s about dressing up.

One year I was sure I would have to cut a Willy Wonka hat out of my son’s hair at the end of the day

There is no disputing that kids love it. No sooner is it over than mine start planning next year’s costumes – their ideas are always insanely overambitious, and usually only tangentially related to books. Has Sonic the Hedgehog ever appeared in print? Could I perhaps construct his spiky blue head using egg cartons? These are the questions I find myself grappling with approximately 15 minutes before we need to leave for school. One year I was sure I would have to cut a Willy Wonka hat out of my son’s hair at the end of the day, as we hadn’t allowed any time for the glue to dry.

Of course, an impressive number of parents do manage to spend hours lovingly hand-crafting costumes. (Generally they have reception-aged children, and haven’t yet worked out the life hacks needed to avoid this kind of thing. Guys: invest in an all-purpose pair of glasses. As long as you have a Sharpie and can approximate a lightning strike – bingo!) Last year I was particularly impressed by the boy who came to school dressed as a giant atlas, complete with geographically accurate maps. Still not sure how he managed to sit down, though.

Such heroic parental effort is not, alas, always fully appreciated by the kids. One friend spent ages last year putting together a brilliant Gangsta Granny costume, only for it to be discarded, swag and all, at the school gates (the wig was too itchy).

Of course, as a booky person I am fully in favour of any initiative aimed at turning kids on to reading. With 800 libraries having closed down since 2010, and attention spans dwindling at an alarming rate, books need all the help they can get in the multimedia age.

I do, however, have a problem with the fact that World Book Day has become yet another opportunity for supermarkets to flog fancy dress to well-intentioned, time-poor parents. The internet overflows with “World Book Day special offers”: cheap, polyester Elsa dresses (hello, Frozen is a film) and Dennis the Menace jumpers (OK, for the sake of a quiet life let’s allow a comic). Many of these will be worn once, and then spend the next couple of decades mouldering in landfill.

Grownups, let’s try to remember, today of all days, that reading is not an end in itself. We read in order to become more conscious of the world outside our own narrow experience; we read in order to think more deeply. The attitude of a reader is the very antithesis of the rapacious, selfish short-sightedness of late-stage capitalism. Here’s an idea: save your pennies on the costume, and invest in a book or two instead.

• Alice O'Keeffe is a literary critic and journalist, and author of On the Up