Me and a friend are going to co-author a book!
Once he gets out of the psychiatric ward where he currently is, that is
How exactly can two people go about writing one book together?
Does anyone know, or have any ideas?
I mean, what are the actual mechanics of doing so?
Basically, what is the best way to do this?
Does anyone here know?
I suggest using Microsoft Teams software, and I suggest combining that with archiving software such as Git. Then you can both work on your document simultaneously in Teams, and you can consult older versions of your work using Git. Git will take a few hours to learn. Teams is included with a Microsoft license, and its somewhat like having a chat and messaging system inside of your word processor. You can also use audio and video as you work on your document. If you prefer to save money, you can use a shared Google docs document.
Before you begin, consult an attorney. "Good fences make good neighbors." If you keep backups in Git and keep regular backups also of your hard drives in a way that is provable and acceptable in court then you will have a good fence. Neither of you will be able to claim sole ownership of the copyright.
There are other software systems of course. I'm only mentioning one combination which could work for you. I think one drawback of Microsoft Word is that it doesn't have much support for chapters and themes. There are programs specifically for writers which do. What I mean is there are programs like Scrivener, but these aren't designed with multiple writers in mind. What they do is help you build up themes and plots and integrate them and build chapters.
Another option is a wiki, which is a web page that you can both edit.