ePub with Images
I downloaded "Myths and Legends of Ancient Greece and Rome" by E.M. Berens from the Gutenberg Library in ePub format. I proceeded to add cover art to the file by converting the ePub to ePub using calibre.
When I began reading the book, I found that the images were overlapping the text. At first I thought the Kobo was at fault, but I opened the ePub in Calibre and it exhibits the same symptoms.
I went back to the original ePub I downloaded, and that version is fine. The images do not overlap the text, but appear to be displayed with the wrong aspect ratio.
It's almost as though calibre corrected the aspect ratio of the images without correcting the space required to display them. I don't know much about the ePub format, but this seems to be a bug in the way calibre converts ePub files with images.