This is Textbook, the mod that allows you to import books from text files (and your clipboard) and export books to text files.
To use it, you'll need to get a Book and Quill and open it up. There will be some new buttons there, one to import from clipboard and the other to import from file. It is important to note that importing will overwrite anything that is already written. Once you've imported, if the file you've chosen exceeds the vanilla 100-page limit, you have the option to split the book into volumes by choosing which volume you want this book to be. You don't have to do this, but use caution with over-limit books on servers, as they could consider this cheating. If you want to write another volume, you'll need to repeat the process and select another volume number. To export a book to a file, open it and choose the Export to file button, then choose where you want to write it to.
Forge: Requires Annotated DI and Fireplace Lib
Fabric: Requires Fireplace Lib
This mod is client side only, so you can use it on servers that don't have the mod installed. It goes well with Audiobook.
To report issues or request new features, use the issue tracker. Do not ask me to port to different Minecraft versions. For questions and other discussion, feel free to join my Discord.
Q: Can you port to 1.14.4 or older?
Mod Spotlight (with Audiobook): https://www.youtube.com/watch?v=95iM8z_YiPQ