> it only downloads the first and the
> last chapters of each fanfic. What am i doing wrong?
Nothing.

Assassin's Love Chapter 1 is
<http://www.fanfiction.net/s/6150313/1/Assassins_Love>
On that page there are NO links to chapter 2.
Only a button 'Next' with an onClick attribute. Httrack does not click on
forms so there's no chapter 2.

The web master is stupid. When they do things like this, Search engines can't
spider the site and their search results place the site very low.