Extracting an epub from an iPhone app is easy. First you unzip the .ipa file. Then you cd to Payload/*/book. Finally, you zip up the files to an .epub file: zip -X ~/book.epub mimetype && zip -r9DX ~/book.epub META-INF OEBPS.
mimetype must be first in the archive for validity, which you can test with EpubCheck.
They are in multi-file HTML format inside the APK, so this is even cheaper and given I wanted them on the Android phone/tablet anyway, easier.
Even better the eBook app O'Reilly delivers has an "Export to ePub" button that will send it to an ePub on your sdcard.
Oh well, it only set me back 5 bucks.