The standard for pirated comic books seems to be a .cbz/.cbr format, as well as a less frequent epub. .pdf is being a discouraged (some would say unforgivable) option but not unheard of in the pirate-web-o-sphere.
The question is, is there an industry standard used by official publishers for digital comic books?
First of all, the .CB* file format isn't a own file format at all, as it simply represents a standard archive file. That's also where the different endings come from:
and so on...
Those are also the most widely used file formats for comics. But serveral publishers use PDF files along with their security features to sell comic books (as far as I observed, those PDFs are largely disliked by many comic fans)
So to speak for reaching the audience, .cb* should be the best option currently available although it unfortunately isn't a standard fully applied by the industry.
