Tesco's recent announcement that sales of books grew by 52% in its latest financial year (to 25 February 2006) should be good news. But in the book business there is no such thing as a silver lining without a cloud. Publishers fret that supermarket power will squeeze profits; high street booksellers fear that book buyers are now accustomed to low prices; while the literati are concerned that the multiples force publishers to focus only on bestsellers.

But it is hard to argue with the numbers. The UK book market grew by 6% in 2005, according to data from Book Marketing, and it was the supermarkets leading the way, up by 41%. Tesco sold 20 million books over the year, taking roughly 6% of the market in 2005.

The big books are meat and drink to the multiples, but the truth is that supermarkets have made a concerted push into 'real' bookselling, no longer restricting themselves to cheap paperbacks, cookery books and children's books. As 2006 looks as though it will be lacking a stand-out bestseller - new titles from JK Rowling and Dan Brown not being due until next year - this tests supermarkets' commitment.

Sainsbury is the latest to devote more space to books, with 120 stores now lined up to carry larger book ranges, such as literary fiction, crime and travel. A recent Tesco bestseller chart had Kate Moss's Labyrinth as its number one, while Asda has been selling Booker winner The Sea among a small range of literary titles.

The traditional book business has been caught on the hop. Sales at high street booksellers Waterstone's, Ottakar's and Borders hit the wall in the latter half of 2005. The first two are now set on a merger driven by the need for sufficient scale to compete on equal terms with the supermarkets. Borders has replaced its MD (with a chief executive), but has also just lost a senior member of its books buying team, inevitably to Tesco.

And the independents have also been hit, with The Bookseller reporting that six independent booksellers had closed their doors.

Price is just one reason why the multiples are selling more books than ever before and plan to sell more. Waterstone's, for one, believes it has something to learn: last week it poached Asda's books buyer.