Originally Posted by SarahMB
So besides the higher resolution readers, are there additional reasons to use larger images?
Future, zooming and archive.
Future: Most readers may be 600×800 today, but who knows what will be the norm in 5-10 years? Would you like to redo your book, re-scan the images, re-process them to adapt them to better screens?
Zooming: Some readers allow zooming of images, and I hope more readers will join. That means you should not feel limited by the screen size and resolution.
Archive: A low-resolution version of an image may be good enough for casual viewing, but some users may want a better version to observe smaller details, or for other uses.