Conde Nast’s tech blog Ars Technica published a Kindle Single by author John Siracusa reviewing Apple’s new OS X Lion operating system. The $4.99 book has 27 pages and all of the content contained in it is available for free online.

According the Nieman Journalism Lab, Ars Technica editor Ken Fisher said they had sold 3,000 copies of  the eBook in 24 hours. The Kindle Single is an eBook format between 10,000 and 30,000 words – or about 30-90 pages – that comes with a lower price tag than a typical book.

Fisher explained in the interview: “I was surprised by how many people told us they read the review online and they just wanted their own copy to go back to. Or they just bought it as a tip-jar kind of thing.” (Via Publisher’s Weekly and GigaOM)