Readers around the world cooed last month when a Welsh bookseller announced he was giving away his shop to a regular customer. It was a lovely story, but as an ex-bookseller of five years, I could only dwell on the harsh realities this unsuspecting man would inherit: slow days, stocktaking and, unavoidably, a few regular oddballs.

Bookselling has been relentlessly romanticised, most often by Hollywood: in truth, it is further away from You’ve Got Mail (Tom Hanks’s snazzy shop Fox Books would have been toppled by the internet) and much closer to that moment in Notting Hill when Hugh Grant catches Dylan Moran ferreting away a book in his pants. This actually happened at a bookshop I worked in: a man was caught packing his trousers with true crime and was asked (amazingly politely) to hand them over to a long-suffering colleague (they went promptly back on the shelf).

Even the grimier portrayals like Bernard Black – Moran’s later turn behind the till in UK TV comedy Black Books – are not that accurate. Yes, booksellers do often hate you, probably because you only know that the book has a blue cover. No, we could never say it because, unlike in Bernard’s shop, there is always an overbearing senior manager hovering nearby. Even the Yorkshire Dales “bookseller from hell”, who lived gloriously free from corporate bigwigs reminding him that the customer was always right, quit his shop after outrage over his policy of charging customers 50p to browse.

Ask booksellers to recall their worst moments in the job and they never have anything to do with books. Those are all to do with customers, who too often bluster in with the air of having read everything on the shelves, but are also unable to tell you the title, author or even the appearance of the book they are after (“I think it is blue” is often, remarkably, enough for a good bookseller to figure it out). One ex-bookseller told me about a woman who briskly informed him that her son had pooed in the children’s department and left without apologising. He did get a sorry from a man after his wife’s waters broke in the travel section.

Stray bodily fluids are by no means a unique treat for booksellers – but anyone who has sold books in the last decade must also deal with: never-ending questions about why it is cheaper online; constant jibes about losing your job to Amazon; cavalier parents who treat your children’s department like a creche; older (usually male) customers who only ask you about books to test your (they hope) comparatively measly knowledge; and hundreds of inane queries about bathrooms, loyalty cards and coffee shops, when, really, all you want to talk about is books.

But there are joys. The customers who ask for you by name because of your shared tastes – especially the ones who come back just to tell you they enjoyed your last recommendation. The romantic opportunities with similar souls (bookshops are wonderful hubs of romance). And, most of all, in between the horrendous stocktaking nights and the ridiculous customers, there is the gentle, constant warmth of being among books, the most ineffable, restorative energy in the world. And the aforementioned ex-bookseller, who cleaned both excrement and amniotic fluid from his shop, also boasted that Harold Pinter once smacked him with his cane. You don’t get that in Topshop.

So seize this Saturday’s Bookshop Day as a chance to say thank you to your booksellers. You never know whose pants they’ve just had to rummage in.

• Sian Cain is the online books editor at the Guardian.