As a New York judge prepares to rule on its legitimacy, Philip Jones explains why the search engine's digitisation of millions of books has huge implications for the books world

In the first half of 2010, if all goes to plan, the world's dominant search engine, Google, will begin to sell online access to somewhere between 5m and 6m books, which it has taken off library shelves, dug out of secondhand bookshops, borrowed from university deposits and digitised – in large part against the wishes of authors and publishers across the world.

It's impossible to overstate the impact the deal – cooked up a year ago between US publishers and authors and Google – could have on our lives, if it is approved by a New York court next month.

Users of the world wide web will be able to call on reserves of published content they've simply never had access to online before. Google will become the world's largest library, albeit a virtual one. It could also become the world's biggest bookseller.

Though the arrangement is applicable only in the US, such are the issues under discussion that the European Commission is this week having a week-long series of meetings in order to try and come up with copyright reform to do something similar – or, in the words of the two commissioners in charge of this process, give every citizen access to "books that today lie hidden on dusty shelves".

But note the qualifying words. There is no guarantee yet that the deal will be approved. The deadline for final objections expired yesterday, before a "Fairness Hearing", which will either approve or throw out the deal, takes place on 7 October. And if you think the objections are mere window-dressing, take note of who has spoken out against the deal so far: Amazon, Microsoft, Yahoo and the German and French governments, as well as authors and their heirs, including the estates of Philip K Dick and John Steinbeck. The settlement is under investigation by the US Justice Department.

So why is the deal so controversial? Google has inverted copyright law by asking rights holders to opt out, rather than opt in. The deal sets Google up as the world's custodian of published content, with no one else even close, or likely to get close – Microsoft gave up its book-scanning programme a couple of years ago, while Europeana, the EU's digital library, has so far only managed to archive 5% of the Europe's digital content, half of this coming from just one country, France.

For Google the goal was always clear: in hoovering up as much published content as it could get its hands on, it not only delivers on its core mission, but also creates compelling web pages around which to sell advertising and harvest user information, which it can sell to third parties. By keeping the content within its database, even where the rights-holder has made the book private, it will also be able to improve its search methodology. As some authors have argued, the sums being offered by Google are tiny in comparison to what it could gain.

Yet it is hard to disagree with Google when it argues that readers will be the main beneficiaries. Google will be able to create limitless opportunities for lovers of literature: Six million books is more than anyone could read in a lifetime, but if Google gets the design of its Book Search pages right, enthusiastic readers could be mining a rich a seam of content in niche areas for years.

It's no wonder booksellers, particularly Amazon, are concerned. But it is not a given that Google will be able to turn its undoubted skills at indexing content into something more commercial, or even useful. Google's current Book Search home pages, which feature fuzzy book covers for titles such as Eastern Trees and Forced Native Labour in Sixteenth-Century Central America, suggest that the search giant has some way to go before it catches up with other online booksellers. And just a week ago the Times Higher Education Supplement called the Google Book Search a "disaster for scholars". A search on "Internet" in books published before 1950 produced 527 results; "Charles Dickens" turned up 182 results for publications before he was born 1812.

After readers, the main party to gain from Google is likely to be authors, even if some might be downcast at the thought of 6m competing books suddenly entering the marketplace. Authors will use the Book Search to generate new ideas, and track reader trends, as they currently do on Amazon.

For publishers, the Google deal represents what one described recently as the least-worst solution. Though some may bristle at its initial tactics, it was always going to be far better to have Google working with them towards a goal that they at least have a semblance of control over, than carrying on its digitisation programme unfettered.

And even those who still decry the deal recognise that copyright law, particularly in respect of those books where no rights-holder exists, is no longer helpful. Even if the Google Settlement is somehow held up in the New York courts, the deal has undoubtedly set the books world on a course from which it will not now be able to deviate. The problem for everyone – and this might even include Google – is that no one yet knows where the journey ends.