Updating build instructions for book

Author: simonsan

README.md

@@ -81,10 +81,17 @@ Correction and elaboration PRs are very welcome.
 
 ## Building with mdbook
 
-Install `mdbook` with the following command
+This book is built with [mdbook](https://rust-lang.github.io/mdBook/). You can install it by running `cargo install mdbook`.
 
-`cargo install mdbook`
+If you want to build it locally you can run one of these two commands in the root directory of the repository:
 
-and run `mdbook build` in the root directory of the repository. The standard
-output folder is `/book`. If you want to take a look in the browser you can 
-use `mdbook serve` and open the corresponding address (take a look at the terminal output).
+- `mdbook build`
+
+  Builds static html pages as output and place them in the `/book` directory by default.
+
+- `mdbook serve`
+
+  Serves the book at `http://localhost:3000` (port is changeable, take a look at the terminal output 
+  to be sure) and reloads the browser when a change occurs.
+  
+