The init command
There is some minimal boilerplate that is the same for every new book. It's for this purpose that mdBook includes an init command.
The init command is used like this:
mdbook init
When using the init command for the first time, a couple of files will be set up for you:
book-test/
├── book
└── src
    ├── chapter_1.md
    └── SUMMARY.md
- 
The
srcdirectory is were you write your book in markdown. It contains all the source files, configuration files, etc. - 
The
bookdirectory is where your book is rendered. All the output is ready to be uploaded to a server to be seen by your audience. - 
The
SUMMARY.mdfile is the most important file, it's the skeleton of your book and is discussed in more detail in another chapter. 
When a SUMMARY.md file already exists, the init command will first parse it and generate the missing files according to the paths used in the SUMMARY.md. This allows you to think and create the whole structure of your book and then let mdBook generate it for you.
Specify a directory
When using the init command, you can also specify a directory, instead of using the current working directory,
by appending a path to the command:
mdbook init path/to/book
--theme
When you use the --theme argument, the default theme will be copied into a directory
called theme in your source directory so that you can modify it.
The theme is selectively overwritten, this means that if you don't want to overwrite a specific file, just delete it and the default file will be used.