Hmmm. I thought I posted this already, so forgive my redundancy:
Epub Support.
Not being involved with the programming, I can rationalize that it "should" be already close - you already open zip files (epub=renamed from zip), so parsing out the peculiarities of epub "should" put it within your grasp.
I know, I know, [ All you do is just... ] is the bane of programming.
But nobody else seems to be anxious to be getting epub onto pocket pc, and this would help with the nitch-carving.......
-bjc