Print book sales were lower than expected at Christmas and the soaring popularity of tablet devices could be to blame, the distributor Smiths News warned yesterday.
Its chief executive Mark Cashmore said book sales in the important pre-Christmas period was "not as strong as we anticipated".
"Is it that we've seen a significant rise in tablet sales?" he asked.
Smiths, which distributes newspapers and magazines as well as books, is still sticking to its full-year profit forecasts as revenues have risen 1.9 per cent since September.
Newspaper sales held steady in value terms thanks to a string of cover price rises by titles such as the Daily Express and Financial Times, even though circulations are down.
But revenues from magazines continued to decline by mid-single-digit percentages.