One of the more memorable and influential library finds for me was an article in _Advertising Age_ which enumerated all of the special characters which should be set so as to accurately communicate, so in addition to en and em dashes it noted:

- − (minus symbol) for use in math equations or to indicate a negative

- I believe it also noted that there were two forms for the hyphen, normal and discretionary

- × (multiplication symbol) for use in dimensions and when actually indicating multiplication

- ′ and ″ (single and double primes) for use when indicating feet and inches, or minutes and seconds

- it also made explicit the difference between º (ordinal o) and ° (degree symbol) and noted when to make use of the other ordinals

- … while available as a special character, it is often better to construct this using suitably sized non-breaking spaces

- © ® ™ ℠ ℗ (copyright and so forth) to indicate such legal constructs as appropriate

- the various spaces en and em space, non-breaking flex space, &c.

I _think_ I still have a photocopy somewhere, but really should find a copy of the actual magazine....

The far more egregious and reprehensible thing is that many books now are published using quite pedestrian typing of the near equivalents from the keyboard as opposed to actually typing the correct signs.

I wrote a bit on this at:

https://tug.org/texshowcase/onetype.pdf

(note that it intended to be printed, folded, cut in the center, then re-folded so as to make a "hot dog" booklet: https://www.makingbooks.com/hotdog.shtml )

EDIT: That said, folks should be sure to get:

https://www.goodreads.com/book/show/41600.The_Mac_is_Not_a_T...

or

https://www.goodreads.com/book/show/358248.The_PC_is_Not_a_T...