There are a wide variety of e-book formats and e-reading devices available. This list is by no means exhaustive; rather, it’s meant to introduce you to the most common formats and e-readers available, as I will be referring to them throughout the book.
1. Plain Text (.txt)
This is the simplest e-book format there is. Although it doesn’t preserve any formatting such as italicized or bold text, it is readable on any computer and files in TXT format are smaller in size than any other format. For the visually-impaired, plain text is the easiest format to read using screen reading software. However, it isn’t very aesthetically pleasing to sighted readers.
2. Hypertext Markup Language (.html, .htm)
If you’ve ever used a web browser such as Internet Explorer, Firefox, or Safari, you’re already familiar with HTML documents. They’re the most basic building block websites use to convey information to visitors. HTML files can be opened in any web browser, though different programs may display the files differently. Stories published on the web that aren’t available for download but are rather meant to be read online are usually in HTML format. You can format HTML files to include italics or bold text, different font sizes, various colors … even images can be displayed in the body of an e-book when saved in HTML format.
Any computer with a web browser will open HTML files. E-books in HTML are easy to read — if the text is too small, you can increase the font size using the browser’s settings, and you can print the file if you want to read it on paper. Some HTML e-books are zipped file archives (ZIP), which include the original HTML file and any images that may be linked in the file. If you download an HTML e-book that isn’t in a ZIP file but instead has the HTML or HTM extension, the images should be hyperlinked to a website or they won’t display properly.
3. Electronic Publication (.epub)
As more e-readers and e-book applications for existing hand-held devices are created, the majority of them are using EPUB as the industry standard.
It’s a free and open format, and in its simplest form, an EPUB file is really a zipped file archive with a different extension. It can be opened using any zip utility such as WinZip or 7Zip. The archive contains all images displayed in the e-book as well as the e-book text contents, which are saved in XML format. There are also two other important files in an EPUB — the OPF (which contains all the book’s metadata, file list, and reading order), and the NCX (which contains the table of contents for all the files). These two files allow e-readers and e-reading software to display chapters in the file as bookmarked links which can be easily accessed by readers.
An EPUB file must be structured in just the right way to ensure it doesn’t contain errors that may prevent the text from displaying properly. There are many tools out there to validate EPUB files, including websites that offer the service to users who want to upload a file to check it for errors. While you can build or edit an EPUB file yourself using ZIP file software, there are programs available that will create a valid EPUB file for you.
Apple’s iBookstore, Barnes & Noble, and Kobo Books are among the distributors who use EPUB files exclusively. If you want to get your book to the widest audience possible, it’s in your best interest to publish in EPUB format.
4. Adobe Portable Document Format (.pdf)
The most common method to transfer documents online is in Adobe Portable Document Format, or PDF. There are two different programs available from Adobe Systems — PDF Reader only allows you to read PDF documents, and is probably already installed on your computer. PDF Creator is the full version of the program which allows you to create and edit PDF files. In the past, you had to dish out a pretty penny to purchase the Creator program or you couldn’t generate your own PDFs. Now, however, there are many free programs available that will make PDF files for you.
PDF files can be compressed, making them smaller in size than other e-book formats. They can contain text and images formatted any way you like — what you see on the screen when you create the book is what will appear in the PDF file once you generate it. This is particularly relevant to authors whose books may contain many images, such as children’s or illustrated books, graphic novels, and comics.
One feature about PDF files that appeals to many authors and publishers is that they can be protected, or “locked.” When you protect a PDF file, you limit what readers can do with the content. You can choose if they can print the pages or save them as text, or if the words on the pages can be read aloud using screen reading software for the visually impaired. While locking the file may protect the content to some extent, it can also limit who may be able to access it.
5. Mobipocket (.mobi or .prc)
Mobipocket e-reading software is available for a variety of platforms, from computers to PDAs to Smartphones. The Franklin eBookman is a hand-held e-reader which only uses the PRC format. The software to create and read Mobipocket files, which commonly have the file extension PRC, is free to download from the company’s website.
With the launch of Amazon’s Kindle, Mobipocket files because more popular with readers because they convert seamlessly to the Kindle environment. If you connect your Kindle to your computer using a USB cable, you can transfer PRC files directly to your hand-held device. If you want to use the wireless feature to move the books, simply rename the file from PRC to MOBI and you can send it to your Kindle account for free — there are no conversion fees charged for the transfer.
The Kindle uses AZW files, which are easily created from PRC files, so if you have any plans to publish e-books on Amazon, create PRC files of your stories first. This will facilitate the process of uploading your book to Amazon’s Kindle service.
6. Microsoft Reader (.lit)
A proprietary program created by Microsoft, the MS Reader can be downloaded to your Windows PC or used on a PDA with a Windows operating system. Reader files are usually DRM-protected and cannot be easily converted into another format. Basically the only readers who can access an LIT file are those who use the MS Reader program.
7. eReader or Palm Digital Media (.pdb)
Palm Digital Media electronic books can be read on a variety of hand-held devices, such as the iPhone, PalmOS, Android, Blackberry, Pocket PC, and both Windows and Macintosh computers. The program used to read PDB files allows readers to bookmark and footnote files, which is a nice feature for those using e-books for reference.
8. Rocketbook (.rb)
RocketBook was one of the earliest stand-alone, hand-held e-reader devices. RB files can be read on RocketBook and Gemstar eBook readers. The format is still used by the eBookWise reader, distributed by Fictionwise (recently acquired by Barnes & Noble).
9. Sony eReader (.lrf)
The Sony eReader uses a proprietary file format called LRF to display content on the device. However, you can find reader software for Linus-based computers that can read LRF files. LRX files are the same as LRF except they are DRM encrypted. Sony eReaders were among the first to be easily found in discount stores such as Target or Best Buy.