I’ve published a few poems in some journals here and there, and have now collected them and many other seriously-workshopped pieces into a self-published book.
Is it appropriate for me to share this news in MPSIMS, with a link?
I assume you’re selling?
Marketplace forum. You need to be a paid member to start a thread there.
Announcements by long term members about publishing a book are permitted, and usually go in MPSIMS. (I’ve made such announcements myself.) However, you shouldn’t provide a link to a place where it can be purchased. For that, you should start a thread in Marketplace (which requires a paid membership).
That’s known as the KellyAnn Conway rule. 
Hands up those who on seeing the topic title felt a momentary alarm, “Oh God, what did I do?”
No, for me it was ‘Oh God, what has XXX done now in Great Debates’?
Vin Diesel posts here?
[sub]though I guess technically that would be xXx[/sub]
“This” is permitted on the board, but don’t confuse it with “that”. They are completely different things.
What about “the other”?
We fear and shun THE OTHER.
SHUN! SHUNNN!
Why MPSIMS? Shouldn’t book discussions (including announcements) be in the Cafe?
If what you want is recognition of a the personal achievement of publishing a book, it goes in MPSIMS. If you want people to discuss the literary value of or critique your book, it could go in CS.
And, as I understand it, if you want to sell the book, it goes into Marketplace. After your membership money goes into the SD Coffers.
(It puts the money in the coffers or it gets the hose again.)
I assumed it was a question about vague thread titles.
Basically what I said in post #3.
Which explains why I understood it. 
And don’t confuse either of them with “those”, which are permitted only when labeled NSFW.
Such things have popped up in the Cafe; it seems a valid place, especially if they’re fiction. (Non-fic on how to fix your car, maybe not so much.)