Более-менее человеческое объяснение новаций EPub 3
In version 2.01 there were three defining documents, the OPF (Open Packaging Format), the OCF (Open Container Format), and the OPS (Open Publications Structure). The OPS referenced a DAISY standard for the NCX file. The new 3.0 standard has 4 defining documents with new names. The OPF becomes the ePub Publications standard. The OCF remains the same and the OPS received the most changes to become the ePub Content Documents. This now includes the old NCX specifications which are no longer used. A fourth document is concerned with Media Overlays and is a new feature of ePub version 3.
В таком виде выглядит вполне ок. Но всё равно движки переделывать ((