[JSWolf]

This may not work well. A lot of eBooks get changed. Even very minor unnoticeable changes. So let's take Project Hail Mary, there are multiple versions of this book. The original has the original cover and another version has a movie cover and there could be other versions.. Also, if anyone makes any chances other then just removing the DRM, and removing DRM can be an issue. There removing watermarks as an option or not you then have a lot more useless signatures. I can see many people creating signatures from eBook they’ve illegally downloaded or calibre made changes to such as updating the metadata.

This can lead to one huge database.