I think either Adam Bryant (organizational psychology at Wharton) or Erin Meyer (same at INSEAD) turned me on to this idea. I think it's generally a good one to (very slightly) accelerate new working relationships to a place of trust, and the emotional pearl-clutching in this thread is interesting to observe.
The best examples I've seen of such manuals (and the best working relationships that have been informed by them) share a common thread: sharing about ourselves where useful,[^1] in order to help others know us better,[^2] and not to control or compel them to do any specific behavioral thing.
So, far from an "instructions [to follow]" (@phoenixy1) or "a one-size-fits-all approach to how different people should act with an individual" (@ralferoo), I think many people intend that the document simply share context in order that you can understand them better, and do whatever you like with the information.
There seems to also be a suggestion that producing such a document is in and of itself a burden to others (@jasoncartwright is very upset about the "arrogance" of even writing one, let alone "expect[ing]" someone to read it, @phoenixy considers them to be a "pretty unreasonable burden"). I can understand the reaction, but I think provided there is no expectation that anyone read it, or that it be a means of controlling or compelling someone to behave a certain way, it's pretty benign overall. (Like, I think everyone would at least once or twice in their careers have access to such a document about some colleague or another, if they thought it were relatively sincere? If so, I say go forth and self-document, just don't have any expectations.)
Here are the sections in mine:
1. Why I have this thing
2. The success criteria for my role, and some general ways I try to achieve them
3. Some general patterns of working (one-on-one cadence, skip mtgs, whatever)
4. Blind spots I have that others have experienced (all verbatim, sought from a mix of new/old colleagues, a few new ones added each year)
5. A few situations where those same people would encourage others to specifically seek me out in a jam (as before, all verbatim yada yada - not necessarily work-related)
6. Work things I love doing / work things that I find stressful (drawn from scenarios the reader will likely encounter)
Of these, 1, 2, 4, 5, and 6 contain precisely zero information relating to my preferences or instructions on "how to" do something. I'm simply providing what I hope to be useful context about me and my role at work. (Assuming you take me at my word that I am not sharing the things I love / things I find stressful for any reason other than you knowing me better.)
The general patterns of working at 3 contains some preferences relating to out of hours contact (along lines of "I don't check my emails or Slack outside of office hours, so you should call or text me if there is an emergency or if a few minutes of my time can save you several hours on something"). Maybe that's somehow outdated now? It's the sort of thing I like to know before I reach out to someone out of hours – a bit like I know some people who appreciate a heads up when visiting a "shoes off" household, so they can wear socks or clip their toenails.
tl;dr I think if you are clear that you have no expectation that anyone even read it, and share relevant, practical context on working together -- with a significant portion sincerely sought from a mixture of people, rather than your own navel-gazing -- these kinds of manuals can be a good shout.
I like reading them, and I like understanding my colleagues better. So I'll tell you that I would enjoy reading yours, and if you ever write one please share it, and that I hope you read mine. That's pretty much it!
[^1]: What constitutes " useful" is of course my determination to make, just as it's your determination to decide that what I shared wasn't useful, and tell me as much.
[^2]: I guess this is predicated on the axiom that understanding your colleagues better is useful. I suspect it is useful -- I think if I had to bet on whether or not any person is more effective in collaborative tasks with a stranger, or with someone they have worked professionally with in any field for several years, I would pick the latter -- although this is uninformed.