I scraped this wiki help page for offline viewing: http://wikihelp.autodesk.com/Revit/enu/2013/Help/00001-Revit_He0
Notice the Side Toolbar -> Revit -> + 2013 -> + Help -> + Revit Help
Click the Plus + icon next to Revit Help and you'll see the drop down for the subfolders.
This tree structure breaks once downloaded for offline use, even though all of the pages are there. The problem is the + Plus icons disappear and/or don't work.
I've uploaded the entire offline directory for reference to my google drive: https://docs.google.com/file/d/0B3nBqdkmyPngX0ZZaWVURGcwQ1k/edit
Can someone help me understand how to fix it?