Great work, extremely useful. After long experiments I managed tot add books. What worked for me was changing the extension from .bin to .zip and than use PeaZip (
https://peazip.github.io/ ) to open it, choos the option: !!! as archive !!!. Then you can go into the assetsfolder and change te content of a text file. Save it. close PeaZip and rename the file again from .zip tot .bin install it on the watch and happy reading. Attention! If you change the filename of a text file you must also change it in the pages.txt !!! Good luck. Many thanks to the developper, we now have the smallest but functional ereader ever!