summary.md updates

guide/src/format/summary.md

@@ -4,66 +4,96 @@ The summary file is used by mdBook to know what chapters to include, in what
 order they should appear, what their hierarchy is and where the source files
 are. Without this file, there is no book.
 
-Even though `SUMMARY.md` is a markdown file, the formatting is very strict to
-allow for easy parsing. Let's see how you should format your `SUMMARY.md` file.
+This markdown file must be named `SUMMARY.md`. Its formatting
+is very strict and must follow the structure outlined below to allow for easy
+parsing. Any element not specified below, be it formatting or textual, is likely
+to be ignored at best, or may cause an error when attempting to build the book.
 
-#### Structure
+### Structure
 
-1. ***Title*** It's common practice to begin with a title, generally <code
-   class="language-markdown"># Summary</code>. But it is not mandatory, the
-   parser just ignores it. So you can too if you feel like it.
-
-2. ***Prefix Chapter*** Before the main numbered chapters you can add a couple
-   of elements that will not be numbered. This is useful for forewords,
-   introductions, etc. There are however some constraints. You can not nest
-   prefix chapters, they should all be on the root level. And you can not add
-   prefix chapters once you have added numbered chapters.
+1. ***Title*** - While optional, it's common practice to begin with a title, generally <code
+   class="language-markdown"># Summary</code>. This is ignored by the parser however, and
+   can be ommitted.
    ```markdown
-   [Title of prefix element](relative/path/to/markdown.md)
+   # Summary
    ```
 
-3. ***Part Title:*** Headers can be used as a title for the following numbered
+1. ***Prefix Chapter*** - Before the main numbered chapters, prefix chapters can be added
+   that will not be numbered. This is useful for forewords,
+   introductions, etc. There are, however, some constraints. Prefix chapters cannot be
+   nested; they should all be on the root level. And you can not add
+   prefix chapters once you have added numbered chapters.
+   ```markdown
+   [A Prefix Chapter](relative/path/to/markdown.md)
+
+   - [First Chapter](relative/path/to/markdown2.md)
+   ```
+
+1. ***Part Title*** - Headers can be used as a title for the following numbered
    chapters. This can be used to logically separate different sections
-   of book. The title is rendered as unclickable text.
+   of the book. The title is rendered as unclickable text.
    Titles are optional, and the numbered chapters can be broken into as many
    parts as desired.
+   ```markdown
+   # My Part Tile
 
-4. ***Numbered Chapter*** Numbered chapters are the main content of the book,
-   they will be numbered and can be nested, resulting in a nice hierarchy
-   (chapters, sub-chapters, etc.)
+   - [First Chapter](relative/path/to/markdown.md)
+   ```
+
+1. ***Numbered Chapter*** - Numbered chapters outline the main content of the book
+   and can be nested, resulting in a nice hierarchy
+   (chapters, sub-chapters, etc.).
    ```markdown
    # Title of Part
 
-   - [Title of the first Chapter](relative/path/to/markdown.md)
-   - [Title of the second Chapter](relative/path/to/markdown2.md)
-      - [Title of a sub Chapter](relative/path/to/markdown3.md)
-
+   - [First Chapter](relative/path/to/markdown.md)
+   - [Second Chapter](relative/path/to/markdown2.md)
+      - [Sub Chapter](relative/path/to/markdown3.md)
 
    # Title of Another Part
 
-   - [More Chapters](relative/path/to/markdown4.md)
+   - [Another Chapter](relative/path/to/markdown4.md)
    ```
-   You can either use `-` or `*` to indicate a numbered chapter.
+   Numbered chapters can be denoted with either `-` or `*`.
 
-5. ***Suffix Chapter*** After the numbered chapters you can add a couple of
-   non-numbered chapters. They are the same as prefix chapters but come after
-   the numbered chapters instead of before.
+1. ***Suffix Chapter*** - Like prefix chapters, suffix chapters are unnumbered, but they come after 
+   numbered chapters.
+   ```markdown
+   - [Last Chapter](relative/path/to/markdown.md)
 
-All other elements are unsupported and will be ignored at best or result in an
-error.
+   [Title of Suffix Chapter](relative/path/to/markdown2.md)
+   ```
 
-#### Other elements
+1. ***Draft chapters*** - Draft chapters are chapters without a file and thus content.
+   The purpose of a draft chapter is to signal future chapters still to be written.
+   Or when still laying out the structure of the book to avoid creating the files
+   while you are still changing the structure of the book a lot.
+   Draft chapters will be rendered in the HTML renderer as disabled links in the table
+   of contents, as you can see for the next chapter in the table of contents on the left.
+   Draft chapters are written like normal chapters but without writing the path to the file.
+   ```markdown
+   - [Draft Chapter]()
+   ```
 
-- ***Separators*** In between chapters you can add a separator. In the HTML renderer
-  this will result in a line being rendered in the table of contents. A separator is
-  a line containing exclusively dashes and at least three of them: `---`.
-- ***Draft chapters*** Draft chapters are chapters without a file and thus content.
-  The purpose of a draft chapter is to signal future chapters still to be written.
-  Or when still laying out the structure of the book to avoid creating the files
-  while you are still changing the structure of the book a lot.
-  Draft chapters will be rendered in the HTML renderer as disabled links in the table
-  of contents, as you can see for the next chapter in the table of contents on the left.
-  Draft chapters are written like normal chapters but without writing the path to the file
-  ```markdown
-  - [Draft chapter]()
-  ```
+1. ***Separators*** - Separators can be added before, in between, and after any other element. They result
+   in an HTML rendered line in the built table of contents.  A separator is
+   a line containing exclusively dashes and at least three of them: `---`.
+   ```markdown
+   # My Part Title
+   
+   [A Prefix Chapter](relative/path/to/markdown.md)
+
+   ---
+
+   - [First Chapter](relative/path/to/markdown2.md)
+   ```
+  
+
+### Example
+
+Below is the markdown source for the `SUMMARY.md` for this guide, with the resulting table
+of contents as rendered to the left.
+
+```markdown
+{{#include ../SUMMARY.md}}
+```