I can't find a way to get two ebooks to build. (Mastering Bitcoin, Mastering Ethereum)
Both projects are based upon asciidoc but using the O'Reilly build tool Atlas.
How can I build this without access to the Atlas tool?
First, kudos to learning about a new tool. (I never heard of it).
The content creation environment is in closed beta, so I wouldn't expect there to be any way to access the source code.
But the reading portal lets you view the full HTML which is generated by the HTMLBook source. I'm guessing that they have a tool to import asciidoc into HTMLbook, but I'm not sure if it only imports a subset of ASCIIDOC elements.
I think the whole point of Atlas is to make it unnecessary to have access to the source code, and to provide readymade templates and styles. Building for epub, pdf and mobi is complex, and it would be hard to recreate their toolchain on your own production environment.
Based on the video I've seen, it looks very impressive and hopefully will be a single source competitor to Adobe Indesign. It's unclear whether storing the source on the cloud will allow you to download an offline copy of the source.
I'm struck by the similarities between Docbook XML and the elements created through the editor. (Indeed, I suspect HTMLBook is based upon it). Even if you downloaded an offline copy on source, I'm unsure how you would build it yourself; (for example, it seems that Atlas uses a commercial PDF processor from AntennaHouse, which most people wouldn't have a license for).
One thing is clear though. If you have access to the HTML output, you could probably import it into some desktop ebook creation tool and change the styles as necessary. The generated HTML is very clean, so I would expect it not to be that painful.
One example of a down-and-dirty export is to paste the HTML output into a MS Word doc, make sure the images are all there and then convert it into a PDF.
Actually you need not access to Oreilly's Atlas, any tool capable of processing Asciidoc files shall fit your needs. If you investigate the Github repository you will find out chapters are in asciidoc, just another markdown format. I introduce you some tools to process *.asciidoc files and create LaTeX, PDF, EPUB, Html and etc.
If you prefer CLI then I suggest using Asciidoctor, included in Ubuntu repositories and can be installed by typing
sudo apt-get install asciidoctor at command prompt. Also if you prefer visual editors give AsciidocFX a try. Besides there is a nice online editor available at AsciidocLive with html export.