Bythell, 38, has long curly hair, glasses and the contented air of someone doing a job so pleasurable that he has ceased to think of it as a job at all. He owns the largest second-hand bookshop in Scotland, the premises composed entirely of nooks and knick-knacks. There's a sheep's skull above the fire, and by the door a collection of walking sticks carved by a tattooed pagan called Sandy. There was, at one time, a human skeleton reading The God Delusion, but that is no longer on display, presumably to make room for more of the other sort of spine. Bythell has a stock of 65,000 titles arranged along a mile of shelving, sometimes in great swathes of colour – Penguins in Irn-Bru orange, Broons annuals in Forth Bridge red.
"The best thing is you never know when you're going to find a nugget of gold," says Bythell. "Last year someone brought me a six-volume set called Audubon's Birds of America which I sold for him at auction, and took a very small cut, for 37,500.
"We do get some extremely interesting customers. There was an octogenarian transvestite who used to trawl the charity shops for books and then drive over here in a Robin Reliant to sell them. I remember him coming in one day and complaining about having to fill in all his complicated benefit forms. He said to me, 'I really resent having to waste my time on those forms. I'm a very busy man-stroke-woman.'"
When Bythell took over the business, his was the only bookshop in Wigtown. Now there are around 20 in a town with a population of 900 people. Most of these are on the Main Street but some are slightly tucked away: Ming Books, for instance, which has the largest stock of crime fiction in the UK, and is locally famous for having a garden patrolled by two geese – Gladstone and Disraeli.
Wigtown's successful bid to become Scotland's official National Book Town was an attempt to regenerate the local economy which had been fractured by the closure of the distillery and creamery. Books were seen as a way of papering over Wigtown's cracks, and it seems to have worked. This year's Wigtown Book Festival runs until October 4, and Main Street, once full of boarded-up shops, a tree growing through a derelict house, is full of life.
On one side of the town square, a conga of primary schoolchildren is passing the stalls of a continental market. "Look at that wee cheese!" exclaims one child. "Are those marbles?" asks another, marvelling at a bucket of olives. On the Mercat Cross steps, a middle-aged man munches a kangaroo burger while reading Kafka.
In the cafe at the back of Reading Lasses, the feminist bookshop, the festival director Adrian Turpin, 39, sips coffee and explains the magic of Wigtown. "What I love about Galloway is it is one of the last unhomogenised places," he says. "Elsewhere in Britain, all the towns are the same, and even the little villages feel like they come out of some Little Village Catalogue. But this area has a real sense of apartness."
Staging a book festival in such a remote part has its challenges. Finding accommodation for authors is one. Getting them here is another. Last year there was "the famous AL Kennedy incident" when, having missed her train, the novelist took a taxi all the way from Glasgow. However, the driver, unfamiliar with the book festival, drove her to Wigton in Cumbria instead.
Kennedy isn't at Wigtown this year, but there are appearances by Roddy Doyle, Iain Banks and Louis de Bernires. There's also a "festival within a festival" featuring whisky-related events at the reopened Bladnoch Distillery, including one exploring which single malts go best with which jazz. Fans of punning will find this rich territory. Glenmorangie Miller? Ardlui Armstrong? Cardhuke Ellington?
Back outside on Main Street, I witness the vrooming arrival of the Veteran Car Club of Great Britain, a convoy of around 40 vehicles dating from before the end of the First World War. It feels like some Chitty Chitty Bang Bang-themed event, but the car enthusiasts are simply visitors keen to get their hands on motoring books. Elizabeth Lawson, 41, has driven from Edinburgh and is busy unscrewing the mascot from her bottle-green 1915 Swift before heading off for a browse. "Old cars and old books go together," she laughs.
There is much pleasure in buying a second-hand book. The fact that they have been read by others is what makes them special. Books are the physical manifestation of human thought and so are more meaningful in their used form than any other pre-owned items. A coat purchased from a charity shop has been on somebody else's back; a second-hand paperback has been in somebody else's mind. It's a much more intimate chain of relationships.
Virginia Woolf wrote about second-hand bookshops as places where one might, by chance, make "sudden capricious friendships" with obscure or vanished authors through buying the books they wrote. But there is something about used books themselves, as objects, that invites human empathy. The language of the trade emphasises this: "Jacket torn, spine creased, slightly foxed." We've all felt that way at times.
Each book, too, has its personal story beyond that printed between its covers. A novel found in Wigtown could have spent its early years in a big city store or even in another country before retiring to rural Galloway. It might have been an unwanted gift but somehow it came to rest in a store in the Scottish countryside, from where, through luck or destiny, it may find the person who will take it home and love it.
That particular narrative arc, so common in books, is beginning to rub off on the population. In one of the stores, a young American woman tells me she came here on holiday last year, fell in love with a bookshop owner and decided to stay. She gave up her job with Nasa, sold all her stuff and flitted from Los Angeles. "People say it's just like Notting Hill," she says, "but in Wigtown."
The town's economic miracle has been written about quite a lot, but what has been overlooked is how the bookshops have boosted the people who run them. They are mostly incomers, lured here on the promise of cheap rents, and sometimes personal crises or a simple desire to make a complete change led them into the business and a new life.
Sitting at a table outside her shop, Reading Lasses, Angela Everitt explains that she and her partner Pam had been working as academics in the north-east of England when they decided to move here. "We had one of those things happen to us that changes your life," she says. "My partner was diagnosed with a terminal brain tumour. So we left Newcastle Poly as it was too stressful, then we were up in Galloway on holiday, we came across Wigtown, and decided to buy a cottage and put our books in it. We opened the shop in December 1997 and she died three months later."
Everitt, 65, wasn't sure whether to carry on with the business. But Wigtown's reaction to Pam's death helped her decide. Locals travelled to Newcastle for the funeral and volunteers kept the shop open for several months until Everitt felt ready to return. "That was just amazing," she recalls. "Wigtown's been very good to me. I've met more homophobia in the social science faculty of an English university than in a small Scottish Presbyterian-cum-Catholic town."
Perhaps there is something about the used book business that makes it attractive to people planning a fresh start. After all, a yellowing paperback, unwanted by its previous owner, is itself seeking a second chance. Also, there's something very gentle about the trade, something soothing and not quite of the modern world. It's hard work carrying boxes, driving long distances to house clearances and so on, but what's bad for the back is often good for the soul.
There isn't a great deal of profit in it; as George Orwell once wrote, "a bookshop is one of the few places where you can hang about for a long time without spending any money". But the booksellers of Wigtown seem a happy bunch, bound together by their passion for the printed word and for a beautiful part of Scotland which, even to many Scots, remains a blank page.
"I don't regret buying this place for a second," says Shaun Bythell, selling me for 2.50 a copy of Hugh MacDiarmid's selected poems. "It's the best thing I ever did."