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O’Reilly Now Sells KF8 Ebooks – Here’s Why You Shouldn’t

A few weeks back Amazon released Kindle Format 8 to the public, and today I learned that a major technical publisher is now selling it.

O’Reilly is one of the shining stars of the ebook world. They were an early advocate of giving the customer what they want: broad format support and no DRM restrictions. They’ve been selling ebooks from their own ebookstore for a long time now, and today they added Amazon’s new ebook format.That wasn’t necessarily a good idea, and I can explain why.

Have you used the new KindleGen tools yet? Well, there’s an interesting quirk to the tools that isn’t readily apparent from the outside.

When you make a KF8 ebook, the output will actually contain up to 3 different ebooks, not one. Seriously, inside that ebook will be one for KF8, another in the regular Kindle format, and if you use an Epub as the source that will be thrown in as well.

As you can imagine, the output is going to be a rather bulky file, and that could be  problem. Size doesn’t matter if you’re submitting the ebook to Amazon (they’ll fix it for you), but if you plan to give it directly to customers then there’s a problem.

Let me give you an example. One of the O’Reilly books I own is a 43 page fact book. That’s a small book, so you would think that the ebooks would be under 100K, right? Well, no. The PDF is 2.3MB, which is not unusual. But the KF8 ebook is 16MB, and that is ridiculously large.

FYI: Kindle (and Epub) ebooks are usually smaller than the related PDF, not 6 times the size.

Now, I might be the only one who cares, but I think everyone should. Those large files are a waste of both bandwidth and storage. All the current Kindles have a finite amount of space, and handing a customer one of these files effectively reduces the storage by 90%. Needless to say, that’s not good.

What’s more, it’s also not necessary (right now). KF8 is currently only supported on the Kindle Fire, and if a KF owner wants the better formatting they can get the Epub and read that with another app.

So if you’re making and selling your own Kindle ebooks, please reconsider not using the new format. At the very least, I would wait until there is a less bulky option. Calibre will eventually support KF8, and it will probably not make such a mess.

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Tom Semple February 9, 2012 um 7:52 pm

If you are submitting content to the Kindle Store, the 'bulk' does not matter: the source archive is stripped off, kf8 devices get only the kf8 content, mobi devices get only the mobi content. (Currently, the Personal Documents service only stores mobi content, and strips kf8 and source archive. Hopefully that will change so both are supported.)

There are readily available scripts to do the same. I don’t know why O’Reilly doesn’t at least strip the source archive, but that’s their decision. I can see why they would not want to separate mobi from kf8 (more formats to manage, from their point of view), but other 'makers and sellers' may choose to do that.

I would not trust calibre to build a high quality mobi file, much less kf8. Fine for personal use, but not for sale.

Nate Hoffelder February 9, 2012 um 8:18 pm

Scripts? Can you link to them, please? This is the first I’ve heard of them (or I would have mentioned them above).

MrLasers May 13, 2012 um 6:01 am

I couldn’t agree more.

Additionally, the "bloat" from the KF8 content is negligible when compared to the Mobi7 version, in extreme cases *maybe* reaching a 25-30% increase. The source files are another matter, usually yielding a 100% increase, but as Tom mentions that is easily stripped out using readily available scripts such as kindle_strip.

Alan February 9, 2012 um 9:29 pm

Size is not an issue for me with cloud storage and with Amazon stripping the source to just the content my device needs. Plus, I have lot of faith in O’Reilly and they have never given me any reason not to trust them. This week I bought one of their just released titles on my Kindle and when I opened it for the first time it gave me the option to upgrade it for a nominal fee ($4.99) so that I got a non-DRM version in multiple formats. Very cool! If all publishers listened to their customers as much as O’Reilly and produces such high quality content we would all be very lucky. When I need a technical book the first place I look is O’Reilly. I might sound like a shill but I assure you that I have no affiliation with O’Reilly other than being a satisfied customer.

Nate Hoffelder February 9, 2012 um 9:35 pm

I don’t like to send stuff via email. Amazon mangles the formatting even on straight Mobi files.

Robert Nagle February 10, 2012 um 11:40 am

Tom, where are those "readily available" scripts?

Tom Semple February 13, 2012 um 9:02 pm

Sorry I didn’t have the info at hand with my previous post. So:


There’s also an experimental calibre plugin to 'split' into separate mobi and kf8 files.

'kindle_strip': this does the simpler task of stripping off the source archive, while leaving the mobi/kf8 segments intact:

I haven’t had a chance to try them yet myself but it looks like the scripts are useable, though there may be some refinements required.

Nate Hoffelder February 16, 2012 um 8:13 pm


Calibre Updated – Now Makes KF8 Kindle eBooks – The Digital Reader May 4, 2012 um 12:36 pm

[…] device or apps.But it’s still a better option than using KindleGen to produce a KF8 ebook; that will give you a bloated file.Calibre /**/ Tags:No Comments so far ↓There are no comments yet…Kick things off by filling […]

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