This is a minimal example for those who plan to write books for Chapman & Hall. Basically you download this repository from Github, fill out the content in R Markdown files, and add more Rmd files as necessary.
Since this example is minimal, it does not cover all technical details (e.g. the Markdown syntax), and you need to read the bookdown book before you write anything that is slightly complicated.
For a full example, you may take a look at the source of the bookdown book, or any books on https://bookdown.org that have public source repositories.