Free ebooks are a popular medium to deliver content across the web. The convenience and the low costs of ebook publishing make ebooks a viable alternative to paper based books.
eBooks in its contemporary avatar made their appearance in the 1970s, when Michael S. Hart of the University of Illinois founded Project Gutenberg, to create electronic copies of technical and scholarly books.
However, it was by 1998, when the US Libraries started to offer free ebooks to the public that ebooks became popular. By 2003, popular fiction and non-fiction works began to spot ebook avatars.
Soon, people who could not publish their books through the conventional publishing route took recourse to the ebook route, and many started releasing free ebooks.
Amazon Kindle, Barnes & Nobles’ Nook, and Sony Reader are the three dominant ebook readers on the market. Most ebook readers use the electronic paper, developed by the E Ink Corporation. This paper allows the display screen to reflect light like ordinary paper, without the need for a backlight.
However, the rising popularity of the iPad and Android tablets makes dedicated ebook readers obsolete. Tablets and iPad use pixel-dense, retina LCDs, which offer a much better output compared to electronic papers. Users may view free ebooks seamlessly in these devices, without having to carry along an additional device.
The ebook market is fragmented, with different ebook readers and tablets operating systems supporting specific formats.
The consortium formed to develop the Open eBook format in the late 1990s recommended a single source-document with subsets of XHTML and CSS, a set of multimedia formats, and an XML schema. It also mandated other specifications, such as cover art and table of contents, which would contribute to standardising ebooks.
In 2007, the International Digital Publishing Forum (IDPF) developed the vendor-independent .epub format. This XML based format has superseded the Open ebook format. .epub is compatible with most ebook readers, including Apple’s iBooks app, Barnes and Noble Nook, Blackberry Playbook, Kobo eReader, and Sony Reader. Amazon Kindle is the only major ebook reader that does not support .epub, as of now.
Apple iPad, powered by the iOS, supports the .ibooks format. While the .ibooks draws from the .epub standard, some difference exists in the CSS tags means that the .ibooks remains incompatible with the .epub open standard. Apple users may create free ebooks using the iBooks Author ebook layout software.
Amazon’s Kindle ebooks, likewise, has its own separate format. Older Kindle eBook readers used the proprietary .azw format, based on the mobipocket standard. The latest free ebooks for Kindle use the .kf8 file format, which supports HTML5, and CSS3. Kindle offers Kindle app to access Kindle ebooks through the iPad.
There are many other standards, such as Netwon ebook (.pkg), Archos Diffusion (.aes), Sony’s Broadback ebooks (.lrf, .lrx), and more. Adobe Portable Document Format (.pdf) remains a popular format for free ebooks in Windows powered devices.