Use the {t} tag to insert story sections that show up in the story's index. For example:
{t}Book 1
Chapter 1: Chapter 1's title
Text for chapter 1....
Chapter 2: Chapter 2's title
text for chapter 2....
{t}Book 2 (or part 2 or whatever division you want to use)
Chapter 3: Chapter 3's title
text for chapter 3....
etc...