Ask HN: Best tool to write book to publish on Amazon/apple/eBook and print/POD

So i am writing a technical book. And i want to get it out to the most places i can. I would like to publish it online as an ebook and print using a Print on demand service.

I have been going through so many posts on HN and other places, but i can't get a easy answer.

The problem i am seeing is, if i use one tool. It will create a good ebook, but wont be good for a POD service, or amazon.

Can anyone recommend a single app for OSX that I can use that will output the final book for EPUB/PDF/MOBI and then can also be used for a Print on demand service. Or if no single tool, maybe a easy process from a single point of writing/editing?

I was playing around with the OSX iBooks Author app which i like, but i am not sure how good that will be with a service to POD and amazon.