Supermarket group Sainsbury’s surprised on Tuesday, a day ahead of its quarterly update, with the acquisition of Anobii, an ebooks service and social network for book lovers.

Supermarket group Sainsbury’s surprised on Tuesday, a day ahead of its quarterly update, with the acquisition of Anobii, an ebooks service and social network for book lovers.

The purchase, for just £1, fits with the retailer’s strategy to carve out greater market share in entertainment following the launch two years ago of a dedicated online business and the launch this year of a music download service.

There’s a much bigger story going on though. Of course JS wants to expand its entertainment offer and the latest deal puts it in partnership with big-hitting publishers that are also Anobii shareholders – HarperCollins, Penguin and Random House UK. But it also epitomises the direction of travel in retail more widely.

Back in the 1990s, the big grocers made a concerted push into general merchandise categories, epitomised by innovations such as the launch of George at Asda or Tesco’s Extra hypermarkets. Their incursion prompted screams of pain from specialists who came under pressure as never before from the biggest kids on the retail block.

The same story is being repeated this decade, but the battleground is increasingly online and the model being pursued is that of Amazon.

Just as Tesco pushed into new categories by extending its in-store offer, Amazon has done the same online. No longer a bookseller, it is a retailer of just about anything and everything – it is the Tesco of the digital age.

Other retailers are following Amazon’s example and recognising that in the era of multichannel and digital retail, traditional product boundaries are collapsing: consumers will buy all sorts of products from a trusted retailer. And as groups such as Tesco replicate Amazon’s Marketplace third-party selling platform, they are becoming sales channels as well as retailers.

Specialist retailers will need to be at the top of their game to retain their connection with shoppers, because the digital revolution is likely to be an even greater transformation than the grocers’ original non-food land-grab.