Ebook Formats

As I’m considering picking up a Nook next month, I’ve been thinking about the possibility of transferring my Kindle books over to it. This has led me to do a bit of research into ebook formats.

First of all, we have the Kindle format, .azw, which is actually just a slightly modified version of the Mobipocket .mobi format with some changes to the DRM and the way the serial number is stored.

And how about the Nook? It supports eReader .pdb and EPUB .epub formats (as well as PDF, but that’s a bit different).

So, how to turn an .azw into an .epub or .pdb ? Well, first you need to turn the .azw into a .mobi. This can be done with the free tool called MobiDeDRM. I have no idea how legal this tool is, so I’m not going to directly link to it or tell you how to use it. But there’s this site called Google that should help you find out all you need to know about it. But I will say that it’s a Python based, command line tool. No fancy UI or anything, but all in all, not too difficult to use. The result is a non-DRM .mobi version of your book.

I’ve actually been using MobileDeDRM for a while, for a couple of reasons:

1. The whole thing where Amazon went and deleted books from users’ Kindles made me want to have a non-Kindle backup.

2. Occasionally I like to use the text-to-speech feature, and this is disabled on many books. By converting it to a .mobi you can get the text-to-speech back, but this sometimes requires some other steps, which I’ll cover below.

Note, I’m not advocating removing DRM for any kind of illegal purposes, such as sharing, torrenting, reselling, or otherwise ripping off the publisher/author/Amazon. But I do believe you have a right to personally use your own purchased content in the way you want, including listening to it, viewing it on another device, and protecting it from being deleted.

Anyway, now you have a non-DRM, .mobi version of your Kindle book. There are two free tools you can use at this point to convert it to something Nook-ready.

1. Calibre. This is a hard core ebook conversion tool. It reads a number of different formats, and though it only ouputs to three (.mobi, .lrf, .epub), it gives you all kinds of options on how to convert, including editing of metadata, look and feel, page layout, chapter detection, and bulk conversion. Generally, the defaults work pretty well. Calibre also deals with images in ebooks pretty well and has some other neat features I haven’t even tried, such as converting RSS feeds to ebooks, and direct device integration.

2. Stanza. This is actually a desktop ebook reader application, but once you load up your ebook into it, you can export it into something like 16 different formats, including .epub and .pdb. The one thing Stanza doesn’t do so well is images. And by “doesn’t do so well” I mean it ignores them. At least in the version I’m using. Not sure if they’ve improved that or plan to. But mainly it’s good for straight text.

So, using either of these tools to convert the .mobi to either .epub or .pdb, you should be able to view these books on a Nook. I did convert a Kindle book down to a .pdb via Stanza and tested it on the Barnes and Noble desktop ebook reader, and that worked fine, which is promising.

As far as enabling text-to-speech, in the few I tested, I converted the Kindle book to .mobi with MobiDeDRM and put that back on the Kindle. While it worked fine, the text-to-speech was still disabled. I think what I did was open up the .mobi in Stanza and re-exported it as another .mobi and put that back on the Kindle, and voila, text-to-speech re-enabled. Unfortunately, this kind of threw off the formatting of the book a bit. The text seemed a lot more squished together. Might want to try that with Calibre, which gives you more control over stuff like that.

At any rate, I think it’s cool to know about all these different formats and how to convert them. Even if you don’t plan to get a Nook or Kindle, you might have another device you want to read books on, with the eReader software, for example. That also takes .pdb files, so the techniques here should work the same way.

More info on various ebook formats here: http://en.wikipedia.org/wiki/Comparison_of_e-book_formats