With independent high street book shops almost extinct, and the larger chains either merging or sacrificing valuable shelf space in favour of coffee bars (and in many cases both) one might be forgiven for thinking that the book publishing industry is in terminal decline.

Nevertheless, publishers are still bringing some 150,000 new titles to the market annually, even though the increasingly powerful supermarkets only stock a few dozen different titles. Even the remaining specialist bookshops only place orders for around 50,000 different titles over the year. Of those only a tiny percentage will get the exposure in seasonal offers that are essential to mainstream success.

Instead, book buyers looking for something beyond the celebrity autobiographies and humour 'gift' titles that will end up in the less discerning Christmas stocking next month will be browsing the virtual shelves of Amazon.

In the absence of a bookshop employee to whom they can address the time honoured question 'is this any good?', they will have to rely on a mixture of newspaper reviews, Amazon's automated recommendation system and with customer choices to pick a winner from the dizzying amount of books on offer.

But who are these customers who take time to leave reviews for others? Apart from optimistic authors operating under a pseudonym, most are written by a comparatively small hardcore of enthusiasts, as evidenced by Amazon's chart of the top 100 reviewers.

Current number one, Peter Harris, has written in the region of 2,500 reviews for Amazon.co.uk. Many of them are posted on Amazon's US site, so his opinions can be read and potentially influence a vast number of English-speaking bookbuyers worldwide.

Just as on recent years 'citizen journalists' have become fệted for their unpaid work on the fringes of the news media, so Amazon reviewers are developing a following of their own. As reviews are flagged as 'helpful' so reviewers gain more kudos, and critically more trust from Amazon's customers.

Their motivations vary. Certainly in Peter Harris' case the initial spur was evangelical. "I started because, as a customer, I found there weren't many reviews for the music I buy and even when there were, they were often brief and uninformative", he said. "I decided to do my bit, hoping it would encourage others to follow. I review more popular stuff too, hoping that more people will notice my reviews and thereby be drawn to the obscure stuff."

Whether customers are grateful to Peter for his recommendations is hard to say, but certainly publishers, for whom the next two months represent half the year's sales, will be glad of any exposure they can get for their books, especially for hard-pressed fiction titles.

Rowan Yapp, an editor at the publishing house, John Murray, is particularly interested in a new Amazon initiative called Vine, which gives selected titles to key reviewers.

She said: "User reviews are, of course, an increasingly valuable resource. . Because it was promoted through Vine, The Interesting Bits: The History You Might Have Missed now has 133 well-considered reviews you can consult before you decide on its worth as a stocking filler. As a browser what's not to like about that level of genuine word-of-mouth?"

Jeff Bell, Vice President of Marketing at Amazon UK, believes that these citizen reviewers, called ‘Vine Voices’, will be of increasing value to both book buyers and the industry as time goes on. He said: “The more content and information we can get on the page to help buyers make their choice the better."

The programme, which only began last month in the UK, has been greeted with positive responses from readers and publishers alike and is expected to expand considerably in 2008. The days of the chap in the bookshop telling you what to take on holiday may be numbered, but the era of the citizen reviewer telling you what he took on his holiday is just beginning.

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