Everything About eBooks & eReaders, Pt 2: eBook Types

In this dawn of the eBook age, as we start to collect eBooks, read them, archive them, and move them around, it's important to understand the different types of eBooks based on their file formats. Thats important because different eReaders only support certain file types.

Once upon a time, there was only one important eReader, the Amazon Kindle. Over time, the Kindle changed its default file format and added new formats that it could display, like PDF. A few other file formats can be converted to also display on the Kindle family.

As the family of eReaders expanded, such as Kobo, Nook, as well as tablets that can display eBooks, the various vendors built book readers that could support some but not all the various eBook formats. For example, Apple's iBooks app for the iPad cannot read (nor does Amazon even allow it by license) eBook files designed for the Kindle. Nor can the Kindle display a very popular eBook standard that Apple and others have adopted -- called EPUB.

These vendor choices are made for a variety of technical and competitive reasons. On top of that, each major ecosystem, Amazon, Apple, etc., adds a security mechanism, by demand from the publishers, called Digital Rights Management (DRM) to the eBook to prevent copying. The net result of this is that if you engage and stick with one of the ecosystems, you won't generally be able to read the eBook on a different platform or directly copy the eBook to a Mac or PC and read it there. (There are exceptions, and this doesn't generally apply to books without DRM.)

However, you may, if authorized, be able to back up your eReader/tablet and include those eBooks and also proliferate the eBook to authorized additional devices. Apple does this with iTunes and the iCloud. Amazon has the Kindle Cloud, and so on. (How you do that will be a future article in this series.)

Managing a Digital Library

Knowing that you may end up being tied to eBooks that are copy protected and able to be read on only one kind of device, you will have some choices to make. Do you want to engage in only non-copy protected eBooks? There are many to chose from, both public domain eBooks, some technical books, self-published eBooks on Amazon.com, and sources that have it in their interest to promote non-copy protected books.

For example, Take Control Books and O'Reilly Books do not apply DRM, and so you can read those books on a Mac, PC or any compatible eReader -- if you select the right file format. Here's a fairly comprehensive resource for DRM-free books.

The advantage of acquiring DRM-free books from the various sources linked to above is that you own the book. You can read it on your Mac/PC, copy it to your tablet or eReader, back it up, carry it forward in time, and it's inheritable.

On the other hand, as I mentioned in Part 1 of this series, books from major publishers sold via Amazon, Apple, Barnes & Noble, etc. ecosystems are harder to manage, and you don't even own them. Worse, electronic measures, kill switches, can remove the eBook from your reader at the copyright holder's discretion.

Also, if you commit to protected books, you may want to take into account the the financial health, commitment and customer service of the various ecosystems. As we know, even very large companies will surge into a product area and then conclude it wasn't for them in the long run.

So whether you restrict yourself to books that are not copy protected with DRM or mix and match both kinds, as you see fit, with the various ecosystems, you need to have a feel for the various file formats so you know how to read them and which eReaders will work.

eBook File formats

  • Mobipocket - Now, just MOBI (and occasionally PRC). This is the original format used by Amazon’s Kindle. It’s proprietary, but if you have a Kindle reader for a tablet, you can read any book in the MOBI format.
  • AZW - Also proprietary, a slightly modified version of MOBI that has better compression. It has DRM capability built in. If the DRM is not used, it's almost the same as MOBI. Modern Kindles use this format.
  • KF8 - Introduced with the Kindle Fire series. It adds HTML5 and CSS3 support and is backwards compatible with previous Amazon formats.
  • CBZ - Comic Book Archive file. Designed for sequential reading of images, like comic books.
  • EPUB - This is an open and evolving standard, maintained by the International Digital Publishing Forum. It’s the one that, for example, Apple’s iBooks and the Barnes & Noble Nook use. (But they also overlay their own DRM.) EPUB is an emerging eBook standard now in version 3. It's designed to flow well on displays of different sizes and shapes, especially as the font size is changed for easier reading. This makes fixed page numbering difficult. If a book is intended to be free, it's likely to be in the EPUB format.
  • PDF - This is a well-known standard document format from Adobe. It has a few problems, however, in support of eBooks as we know them. First, the font size isn’t adjustable. That’s good for authors/publishers who want to preserve the look and feel of their creation, especially when there are embedded drawings, diagrams, etc. But it's not so great for readers who may want to adjust the font size in a book for clarity. Second, it doesn’t flow well, that is, it doesn’t adjust well to varying screen sizes and shapes. If the reader does have the facility to zoom in, it may be hard to see the whole page. On the other hand, unlike EPUB, one can always refer to a fixed page number.

Here's what an Apple PDF document looks like on a Kindle 4. The full page type looks small and is almost unreadable.  If you zoom in, you can't digest the whole page.

A full-page PDF is virtually unreadable on this Kindle 4

This Wikipedia entry discusses some of the other minor eBook formats and also has a chart that explains the features of many of the eBook formats.

eReaders and Formats

There is a highly regarded eReader app for the Mac, Windows and Linux called Calibre. It can read just about any eBook format known to man, and it's free. However, the file must not be copy protected. If your starting point is to build an eBook library on a PC or Mac and only dabble in the eReaders and ecosystems, then this app is a must-have. (But there are others, and TMO has reviewed them.)

If you're planning to buy an eReader or a tablet that has eReader apps, it's helpful to know which ones read which files, especially for those occasions in which you want to move a certain eBook file onto that device. Just as Microsoft's Excel isn't programmed to read Adobe Photoshop files, some eReaders aren't programmed to read certain eBook files.

iBooks Kindle Nook Nexus Kobo Sony
  TXT       BBeB

Amazon also offers a Personal Document Service in which personal documents of certain types can be moved into your cloud of purchases, converted and then loaded onto the desired Kindle. Those supported file formats are:

  • Microsoft Word (.DOC, .DOCX)
  • PDF
  • HTML
  • RTF
  • JPEG
  • GIF
  • PNG

The Nook eReader can also display these types of Microsoft files: DOC, DOCM, DOCX, XLS, XLSM, XLX, PPT, PPS, PPTM, PPSX, PPSM, PPTX.

Here is a screen shot of a PNG file that I uploaded to my Amazon cloud, then directed to my Kindle reader on an iPad 3.

PNG file uploaded, converted, downloaded


Jumping into the world of eBooks and eReaders is, unfortunately, not a carefree affair here at the dawn of the 21st century. There is DRM to contend with. Copy protected books with DRM may not have the desired permanence or flexibility you want. Even unprotected books in a given file format may not be readable on the eReader you bought. There are decisions to be made about who you'll buy or acquire books from and what format you'll want them to be in for the long term. That is, to the extent you are able.

As this series continues, we'll delve into many more of the nuances of the technology that will help with eBook library management and product selection.

Articles in This Series


November 28: "Everything About eBooks & eReaders, Pt 1: Introduction"

November 29: "Everything About eBooks & eReaders, Pt 2: eBook Types."

December 4: "Everything About eBooks & eReaders, Pt 3: Apple's iPad."

December 12: "Everything About eBooks & eReaders, Pt 4: B&N Nook"

December 18: "Everything About eBooks & eReaders, Pt 5: Google Nexus 10"

December 21: "Everything About eBooks & eReaders, Pt 6: Amazon Kindle Fire HD"


Book icon via Bookle