bookdown: Authoring Books with #R Markdown
▻https://bookdown.org/yihui/bookdown
The bookdown package was built on top of R Markdown (▻http://rmarkdown.rstudio.com), and inherited the simplicity of the #Markdown syntax (you can learn the basics in five minutes; see Section 2.1), as well as the possibility of multiple types of output formats (PDF/HTML/Word/…). It also added features like multi-page HTML output, numbering and cross-referencing figures/tables/sections/equations, inserting parts/appendices, and imported the GitBook style (►https://www.gitbook.com) to create elegant and appealing HTML book pages. This book itself is an example of how you can produce a book from a series of R Markdown documents, and both the printed version and the online version can look professional.