Five years ago, the words "book group" were likely to conjure up an image of a kooky collection of misfits, much like those portrayed in Annie Griffin's TV series of the same name. The Channel 4 show, set in Glasgow and featuring a neurotic American, a pretentious, heroin addicted post-graduate and a couple of footballers' wives, portrayed a phenomenon still on the fringes that was driven by social desperation more than by a love of literature.

Fast forward to 2007, and it's a different story. Hundreds of thousands of people across the UK are now thought to belong to a book group. What's more, the groups have moved out of living rooms and libraries and into TV, radio, the internet and newspapers. These new clubs offer recommendations and notes for readers across the country who tackle the same books in tandem.

Leader of the pack is the Richard and Judy book club, set up in 2003 by the champions of daytime television. The pair took their lead from Oprah Winfrey in the US and have impressed critics with a thoughtful, balanced list of modern classics, which are chosen by executive producer Amanda Ross. The club's extra-ordinary power to catapult books up the bestseller list, creating over-night literary sensations, has amazed the publishing industry.

So, perhaps last week's announcement that retailing giant Tesco wants a piece of the book group action should not come as that much of a surprise.

Each month, the supermarket's book club will select a book released by its partner, publisher Random House, and offer notes and reviews in the Tesco magazine and on its website. Tesco aims to make choosing a book as easy as grabbing a tin of beans or a pint of milk. Its initial choices sound interesting and intelligent. Alison Weir's Innocent Traitor, a historical novel about Lady Jane Grey, will kick off proceedings and Scottish novelist Kate Atkinson's One Good Turn will follow.

But some people are sceptical about the homogenising effects of the corporate book group. Could they lead not to the promotion of choice but to a reading culture that is dictated by a tiny minority?

It is a complicated issue, says publishing commentator Danuta Kean. "People were initially very sniffy when Richard and Judy announced plans for the book club. They thought it would be about promoting trash fiction," she says. "But Amanda Ross recognised that people were interested in literary books as well as more commercial ones and the list is a great mix. That can only be a good thing."

But while the club helps raise the profile of books that might otherwise have been missed, it also creates problems. She explains: "As soon as they saw its effect, publishers started looking for books that would be selected for the Richard and Judy list. They are also looking for a recommendation from Waterstone's and to be the hot pick on Amazon."

The result? Publishers can no longer afford to take chances and authors who have enjoyed modest successes over many years are suddenly being dropped in favour of potential big hitters.

"They could be on their way to writing an opus, but will not be given that chance," says Kean. "Ian Rankin, for instance, wasn't an immediate success but his publishers stuck with him because they saw his potential. That wouldn't necessarily happen now."

James Robertson, the Scot whose Testament of Gideon Mack made Richard and Judy's list this year, is a beneficiary of the phenomenon. Sales of the paperback have reportedly reached six figures.

"I knew it was a big deal because my publisher and my agent were very excited but I don't think I appreciated quite what a difference it would make," he admits.

"It's clearly benefited me and I am delighted that the book has reached so many more people than it otherwise would."

Though his own experience has been positive, Robertson has concerns about the book-group trend.

"The downside is that if someone goes into a book shop and buys the books that Richard and Judy have recommended, perhaps they won't buy other titles," he says. "There is no doubt that there are winners and losers in this. That's something I feel slightly disturbed by. There is a sense that it is very much about corporate dealing."

Robertson is not alone in his discomfort over "corporate dealing", according to Cathy Kinnear, manager of an independent bookshop in Glasgow's west end.

"The book clubs are not about giving people choice," she says. "They are actually narrowing it. We can offer recommendations that are targeted at our customers, bearing in mind local preferences rather than picking out a few books for the whole nation."

Though Kinnear's shop is busy with loyal customers, it is one of a dwindling number. Many book shops have been forced out of business by the big discounts that the chains can get from publishers and pass on to readers.

Supermarkets such as Tesco are certain to get cheap deals on the book club titles they are planning to promote, according to Marc Lambert, director of the Scottish Book Trust.

"Supermarkets will all sell some book at a loss," he explains. "It doesn't matter to them. It's just another way of getting you into the store where you're sure to buy something else." He does not, however, believe that the book club trend is all bad. "Generally, I think clubs like the Richard and Judy one are very useful," he adds. "More books are being published than ever before and people looking for a book group choice can easily be bewildered. Recommendations can be a useful signpost."

Mary Greenshields, co-ordinator of adult services for Glasgow Libraries, which runs 25 groups across the city, agrees.

"Our groups are not falling back on the recommendations of book clubs," she says. Most people, she insists, do not buy into the hype, concentrating instead on the classics, translated works and fiction.

The popularity of book groups has led to launch this week of Books to Go, library books in multiple sets that be can borrowed on extended loan by book groups.

"We have some of the Richard and Judy books on that list, as well as ones that have won the Orange or Booker Prizes. But there are all sorts of others as well," says Greenshields.

Professor Jenny Hartley, of Roehampton University, who has researched the rising popularity of book groups says readers can sift useful recommendations from marketing ploys.

"I have heard fears that, as a result of lists produced by publishers, newspapers or Richard and Judy, everyone is reading the same thing," she says. "I think there's snobbery attached. So what if everyone is reading The Da Vinci Code? It was jolly enjoyable. I think that once people get started they can spread their wings and make their own choices as well."

What's on the lists