Just curious. I created a nice EPUB in InDesign, all my images are full-page/screen, 1024x768. I exported it as a fixed-layout EPUB and specified 150ppi to cover the iPad's Retina resolution. However, Apple's iBooks wouldn't accept it due to the pixel dimensions being too large. I had to re-export at 96ppi (which was then accepted on iBooks Store). I was hoping for 144ppi, which would be equivalent to an iPad's retina resolution (2048x1536), but it's not an option in the pulldown menu. Am I off-track here? Any idea if this needs to be addressed? Thank you.
I believe 2MB is the maximum size for an image in iBooks.
Currently InDesign does not let you enter your preferred resolution while exporting. it has to be from the available choices-72,96,150,300 ppi.
To allow the user to be able to pick his own resolution setting is something which is in our backlog for EPUB Enhancements and might get addressed in later updates.