The Scottish Government has spent £800,000 so far meeting the demand for copies of its blueprint for independence.
More than 100,000 copies of the Scotland's Future white paper have been ordered since it was launched last November, with a fourth reprint of the 670-page document now being ordered.
Deputy First Minister Nicola Sturgeon said there had been a "huge level of demand" for the paper, adding this was "testament to the appetite for information that exists around the referendum debate".
Voters in Scotland will decide whether the country should remain part of the UK or not in a ballot on September 18.
The white paper sets out the Scottish Government's proposals for the country to become independent, with approximately £75,000 having been spent producing the document.
A further £350,000 has gone on printing the white paper - which is free to order - while distribution costs so far have amounted to about £375,000.
Ms Sturgeon said: "The white paper is the most comprehensive and detailed blueprint of its kind ever published, not just for Scotland, but for any prospective independent country.
"It is a landmark document which sets out the economic, social and democratic case for independence, and provides the people of Scotland with the answers they need to make an informed choice on September 18 this year."
She added: "We want everyone to have the opportunity to read the white paper and that is why it is free to order.
"It is well worth the cost of delivering it directly into the hands of the voters to ensure the choice they make on September 18 is an informed one.
"Since its launch in November the guide has been a 'bestseller' with over 100,000 copies ordered, and three additional reprints. A fourth reprint has now been ordered to keep pace with demand.
"The huge level of interest in Scotland's Future makes clear that voters want access to information that will allow them to make an informed decision on September 18 and my challenge to opponents of independence is to produce their own detailed prospectus - the people of Scotland deserve nothing less."
Pro-union politicians claimed the bill for of the white paper rose to more than £1.3 million when publicity costs and the expense of producing an easy to read version were factored in.
Liberal Democrat MSP Jim Hume hit out: "This is one holiday bestseller which will quickly be consigned to the bargain bin.
"Taxpayers have already stumped up a £1.3 million advance for the existing copies, but with the SNP's assertions on EU membership and currency falling apart day by day the nationalists are going to have to publish many more revised editions before September.
"We all know that the SNP will say anything to achieve independence. What we didn't know is how much we are paying for them to say it.
"Taxpayers will be fuming that the Scottish Government has spent the equivalent of a lottery win on a document which fails to answer any of their basic questions on independence."
Scottish Conservative deputy leader Jackson Carlaw said the cost of the white paper "would be a considerable spend for a work of fact", adding that the document "must be one of the biggest ever taxpayer-funded investments for a work of fiction".
He said: "The public will feel extremely short-changed over this, particularly given there's only one page on Scotland's economy.
"Alex Salmond himself admitted in the Scottish Parliament chamber that this is a document containing SNP propaganda and it's utterly ridiculous that he should be sanctioning taxpayers' money for this."