The best way to get started working on a Leanpub book is to follow the steps in the comprehensive tutorials we have for each of our writing modes!
It only takes a few minutes to set up a book, and each guide will show you how to get started.
Writing a Leanpub Book
The following article has links to all of our "Getting Started" tutorials for writing a Leanpub book, with a detailed screenshot-by-screenshot walkthrough for each of our book "writing modes":
Quick Walkthroughs for Getting Started on a Leanpub Book
http://help.leanpub.com/en/articles/3088382-quick-walkthroughs-for-getting-started-on-a-leanpub-book
Creating a Leanpub Course
The following article has links to all of our "Getting Started" tutorials for writing a Leanpub course:
Quick Walkthroughs for Getting Started on a Leanpub Course
But I Really Want to Read a Manual!
If you'd like to dive in to the specifics of how Markua, Leanpub's "Markdown for books" plain text markup syntax, here's the manual for you:
The Markua Manual
If you want to write a Leanpub book in plain text, you'll be writing in Markua. Markua is based on CommonMark, which is the best specification of Markdown, and adds a number of extensions for books and courses. The Markua Manual documents the beta version of Markua which is used in Leanpub today.
If you're really into this kind of thing, and you want to see the full spec for Markua (which is ahead of the Leanpub implementation), you can find it at at http://markua.com.
The Leanpub-Flavoured Markdown Manual
This is the manual for old-school Leanpub authors who are writing their books in Leanpub-Flavoured Markdown.