Removing the DRM from my Kindle books
A few months ago, Microsoft made headlines when they announced they’d be turning off people’s books. They were turning off the DRM servers behind their ebook store, and refunding customers for any books they’d bought. I never bought any books from Microsoft, but I do have a collection of Kindle books, and this story was a reminder to investigate ways to remove the DRM from those.
Google suggests that Calibre can do this with the right plugins, but I don’t use Calibre for anything else, and I want to install new software as little as possible. I prefer solutions that use command-line tools and (ideally) run inside Docker container – they tend to be much more portable between machines.
I’ve got a script that works now, which leans on two other tools to do the heavy lifting:
Stripping the DRM: ch33s3w0rm/kindle_dedrm. This is a Python script which strips the DRM from an encrypted Kindle book. The encryption in a given file is tied to your device, so you’ll need your Kindle’s serial number to perform the decryption.
It runs in Python 2, no dependencies required:
$ git clone https://github.com/ch33s3w0rm/kindle_dedrm.git $ cd kindle_dedrm $ python2 kindle_dedrm.py --kindle=<KINDLE_SN> /path/to/encrypted_book.azw
It creates a DRM-free AZW file alongside the original file.
Converting AZW to EPUB: ebook-convert.
The AZW format is Kindle-specific; if I read my books on anything else, I need to create a copy as an EPUB.
There are online converters that take an AZW and return an EPUB, but I feel uncomfortable doing file conversion via a third-party service.
You can do this with the Calibre GUI app, or its bundled command-line tool, ebook-convert. The latter lets you convert ebooks between formats in a script, and that’s what I really want. I found a Docker image that includes Calibre, and I override the entrypoint to invoke the command-line tool:
$ docker run --rm \ --volume $(pwd):$(pwd) \ --entrypoint ebook-convert \ regueiro/calibre-server \ $(pwd)/unencrypted_book.azw unencrypted_book.epub
And now I have two copies of my book: an AZW to use on my Kindle, and an EPUB to use everywhere else.
My script has a couple of extra pieces to upload the files to my ebook manager, which are very specific to my setup – the software I’ve linked above is more general, and hopefully a useful starting point for anybody else who wants to strip the DRM from their Kindle books.