In the time between I last published something through Amazon Kindle and now, Amazon has introduced new tools for e-publishing. They're a dramatic improvement over the earlier toolchain — easier to use, easier to comprehend, and something I can get results from in minutes, not hours.
In the days when dinosaurs roamed the earth and the Kindle was still this awkward thing with a screen that was more charcoal and ashy gray than black and white, the tools Amazon provided for generating Kindle content were these horky command-line things. People wrote scripting to handle the book distillation process, or handed off the work to someone who knew what they were doing. Eventually, GUIs made the job easier — e.g. Calibre, which I used for some time as an intermediary step between my Microsoft Word document and the final stage.
Now Amazon has Kindle Create, and it comes very close to providing a single-step interface for the whole process. You drop in a Microsoft Word document, and use a visual editor to decorate the file with formatting. Chapter headings are automatically deduced from section heads in the document, but you can insert or remove them. Several canned styles are provided with the program, and you can preview how the whole package looks on a variety of emulated devices.
It's also possible to make spot corrections of typos by simply editing the text. In theory you could compose the entire book directly inside Kindle Create, but I'd rather perform the brunt of the work in an application suited to it (you know, like Word).
One tiny drawback of using Kindle Create is that it is intended strictly for distilling Word to Kindle. It doesn't let you produce, say, regular EPUB documents from the resulting file. This frustrated me because one of the other services I've been using, InstaFreebie, accepts EPUB as a format. It would have been nice to use the same program to generate a file consistent across Kindle and InstaFreebie, but now I have to take the same Word doc and distill it twice through two totally separate programs to get roughly the same effect.
This is, however, still light-years better than the crummy toolchain I was struggling with even only a couple of years ago.
Kindle Create isn't open source, but it is free to use. I'm still going to keep Calibre around for edge cases like InstaFreebie, but I'm considering republishing all my previous work through Kindle Create to make it stylistically consistent, and also to provide a proper workflow for fixing all the problems that tend to bubble up (typos, etc).