EPUB won't open on my e-reader

[digitalgutenberg]

The epub versions of this book won’t load on my old Bebook Club e-reader. The following error message is displayed: "Cannot open the document, Load Error".

After editing the epub file and deleting the images, the file would load without any issues. At first I thought the svg files somehow were blocking the file from loading, but apparently this isn’t the case, svg support has always been a part of the epub specification. (I tried to embed a basic svg in an empty epub file, and it would load without issues, so the svg files aren’t the problem here.)

Instead it is most likely the sheer size of the bitmap images that is the problem here, the bitmaps seem to be optimized for print, not for e-readers.

To illustrate the issue: “1641.png” is actually a grainy screenshot, but somehow it has a resolution of more than 8900 x 4900 and is 6.8 mb. To put this into perspective, the resolution of my e-reader is 800 x 600.

“1612.png” is yet another screenshot, and although it’s merely 400 kb in size, it has a resolution of more than 12000 x 5000. The majority of the bitmaps (with the exception of those in the nb folder) likewise seem to be massively oversized.

Another thing I might mention is that the images files in the “nb” folder are duplicated, they come as both png and svg. I’m not sure if this was intended.

Generally speaking my e-reader doesn’t like too big files, and this is also sometimes the case when it comes to pure text files.