Originally Posted by slayda
I agree with NatCh's comments in general but am more skeptical that there is sufficient space in a typical image to "hide" a full book's text, especially since some books include additional images.
Also, JPEG (in general) is a lossy compression technique. There is one version that is not lossy but that is typically not used for most JPEG images and is definitely not compressed as small as the lossy ones. With images the lossyness may not be noticeable but it probably would with the text. However there are lossless image formats that could be used, e.g. GIF, TIFF.
It was all fun & games during my youth.
Now it would just be work.
TIFF has no compression at all but supports several compression themes including GIF as an option. PNG is a non-lossy compression you might have been thinking of.