The ../page/X structure ties to pagination, not to post names. I'm sure you could change them but I'm not sure how deep the effects of the change would be.
Have you thought about an alternate solution?
Name each post your chapter name
- Chapter 1
- Chapter 2
Add a plugin that adds previous / next navigation functionality each individual post. Something like WP Post Navigation. That way, when someone finishes reading the first chapter, there will be a link to navigate to the next.
You could change your url structure to fit your needs. For example, if you wanted the structure to look like
http://yoursite.com/chapter-1, etc. you'd just have to change the permalink settings to 'post name' (Admin > Settings > Permalinks).