Reading ePub formatThe EPUB format brings together a bunch of different specifications / formats: one to say what the content of the book should look like (a subset of XHTML 1.1 + CSS) one to define a "manifest" that lists all of the files that make up that content (OPF, which is an XML file) one to define how everything is packaged up (OEBPS: a zip file of everything in the manifest plus a few extra files) The spec
