Search giant Google is facing its opponents in a New York court over long-delayed plans to create the world’s largest online library.
The fairness hearing has been set up to listen to arguments for and against a controversial deal between Google and US authors and publishers.
Critics say the pact would hand the search giant a monopoly over online books sales.
Some 26 interested parties will be given time to outline any objections.
"This case is the key showdown. It’s high-noon time in front of a judge," said John Simpson of Consumer Watchdog, one of the groups that objects to the settlement.
"I do think all the books in the world should be digitised, but I think it is completely wrong to give one huge company control of that huge database and this is a very, very important matter," Mr Simpson said.
The 26 interested parties who have filed briefs in the case have been given just five minutes to state their arguments.
Consumer Watchdog will be joined by the Open Book Alliance, a consortium that represents several organisations opposed to the deal, including Amazon, Microsoft and Yahoo!.
In its brief, the Alliance said: "Google is focused on becoming the sole owners of an immense digital library that will improve the company’s advertising-based search business.
"This de facto exclusive licence will provide Google with an enormous advantage over its search competitors."
Other critics who will be given an opportunity to speak include representatives of Germany, France and the state of Connecticut.
Google’s original plan to digitise millions of books worldwide first ran into trouble in 2004 when the Authors Guild of America and the Association of American Publishers sued over "massive copyright infringement".
A deal was thrashed out in 2005 whereby Google agreed it would pay $125m (£77m) to create a Book Rights Registry where authors and publishers could register their works and receive compensation. At stake are the rights to over 25m books.
This scheme needed court approval and after a year of delays a date was set for October 2009. Judge Denny Chin postponed that following a plethora of criticism and opposition.
Since then Google has amended the agreement but not enough to assuage the likes of the Department of Justice, which said it "still confers significant and possibly anti-competitive advantages on Google as a single entity".
In its own 67-page filing, the search giant said "approval of the settlement will open the virtual doors to the greatest library in history. To deny the settlement will keep those library doors locked".
Google spokesman Gabriel Stricker told BBC News the company remained hopeful of winning final approval
Google wanted to "realise the goal of significantly expanding online access to works through Google book search, an ambitious effort to make millions of books searchable via the web", he said.
Judge Chin is not expected to make an immediate decision on the case.