While the Best Practices document (over in the Adobe Developer Connection) had the recommendation that books be broken up into chapters, it wasn’t clear when you needed to break a document up further, or when a book was small enough so that one XHTML file was sufficient.
With the recent update to the document (version 1.0.2) we’ve given you information on how big the chapters can be.
Those limits on the file sizes are as follows:* XHTML/DTBook chapters: 300k uncompressed per chapter/100k compressed.* Images: 10M uncompressed.Note that these limits are for a single chapter document (or image) within the package, not a limitation on the size of the ePub document. The ePub can of course be much larger (limited by available storage space.)The limits are important for reading ePub documents on a mobile device.