I had a question about optimizing an ePUB for a particular device. Recently, I completed two different training videos for fixed-layout and flowable ePUBs for InDesign CC. In both videos, the instructor indicated that an ePUB had to be optimized for a device.
I can understand the need to optimize for a particular eReader, such as iBooks, Readium, etc. since each of these interpret the CSS a little differently. What I don't understand is why do you have to optimize for a device? I never see ePUBs for sale on iBooks, Google PlayBooks or Kobo that are specifically for for a device like an iPad or Kobo Glo.
I'd be grateful if anyone would shed some light on this for me.