Thanks for taking a look. I changed my command line to the following:

httrack <http://iphone-3d-programming.labs.oreilly.com/> 
-O "/Volumes/DATA/filestore/httrack/iphone-3d-programming.labs.oreilly.com/" 
-s1 
-%c1 
-A2000 
-%A "jpg=image/jpeg" "
+*iphone-3d-programming.labs.oreilly.com/

I still have the same result where the jpg, css and png files are not saved.