You can get $5 O'Reilly EPUBs from the App Store everyday.
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.
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.