Use
Markdown or
Textile to mark your chapter headings, e.g.
Code:
Title
======
## Chapter 1
## Chapter 2
Then change your chapter xpath under structure detection to use only h1/h2 tags:
Code:
//*[name()='h1' or name()='h2']
If you don't want to edit the text files give heuristics a shot, it will find them automatically for a lot of cases.