I had a quick look at the update.
First, the Spanish and Australian downloads are identical.
Second, there's two new files in this update:
Last, 58 files are different between this and the previous update. Of these, 17 were mostly empty jar/zip files. 33 are the same size, but the binary contents are different - most of these are in the framework directory. 8 files are different sizes. These are:
Old New File
177864 177814 app/EbookHome.apk
3411227 3413821 app/EbookNetworkApplications.apk
589312 589952 app/EbookNetworkApplications.odex
639788 639789 app/EbookReader.apk
1025800 1026696 app/EbookReader.odex
53606 55285 etc/NOTICE.html.gz
666228 670324 lib/libcrypto.so
159108 159132 lib/libssl.so
Is there enough of a size difference for EbookReader.odex that there might be some bug fixes in the reader app? This size differences (almost nothing) for EbookHome.apk and EbookReader.apk seem to indicate no real change.
Not sure what all this proves, but it passed half an hour this afternoon