LaTeX cookbook?

There's a LaTex wikibook which attempts to be something like what you describe. I've found it very useful in the time it's been around, and recommend it highly.

FWIW, I'm not connected to the project in any way, just a happy reader.

Yes, there is a 378 page book titled "LaTeX Cookbook" published by PACKT Publishing (2015) written by Stefan Kottwitz. I downloaded the free sample ebook edition, and based on the table of contents, it looks like an excellent resource.

Tim Arnold tried to get one kind of cookbook to go but it never took off. Too bad.