Yes, just those four files is fine. I found the same as you did, no secrep.xml or the .unload file but when I restored the files I did have after a hard reset MS Reader was still activated.
There hasn't been any change with MS Reader for a couple of years and it really shows. It barely supports VGA devices (*really* stupidly large font sizes) and has a lot of issues with books on SD or CF card in that if the card takes to long to re-register with the system when it comes out of standby then MS Reader will whine like a schoolgirl until you exit it and reopen the book, almost *every* other ebook type application I've seen handles this better than MS Reader.
It also has a very perverse book selection system that is an absolute nightmare if you have more than 5 books loaded on to your device... which I often do, my CF card has about 50 books ready for me to read at any given time...
Might I recommend Amber Convert LIT (
http://www.processtext.com/abclit.html) to convert your books to another format and something like Haalireader (
http://haali.cs.msu.ru/pocketpc/) for a lightweight book reader. If you use Haalireader then it supports the FB2 format the Amber can put out.