Fetch the [gourou](https://github.com/SamuelMarks/libgourou) library and it's util scripts, use a `.acsm` file to download the encrypted `.epub` and then remove the encryption. Requires an account at [account.adobe.com](https://account.adobe.com/), sadly.
```bash
yay -S gourou # if you're on arch linux with yay
adept_activate -u <your adobe email> # then enter your password
acsmdownloader -f The_Mercy_of_Gods-epub.acsm # I got my .acsm file from Google, where I bought the book
adept_remove -f The\ Mercy\ of\ Gods.epub
```
Congratulations, you have successfully de-eviled a book. Enjoy it wherever you want!