Digital gifts read well at Quercus E-books made up 25 per cent of sales at Quercus, the Girl With The Dragon Tattoo publisher, during the first three months of the year, in yet another sign that digital adoption is growing fast. Quercus chief executive Mark Smith said e-book buying was seasonal, with sales spiking after Christmas when people received Kindles and other e-reading devices as gifts. E-books continued to sell heavily in the first three months of 2012 but sales have slowed since then. They represented 11 per cent of group turnover last year and should reach 17 to 20 per cent this year.