Nothing much happened
roughtype.com
roughtype.com
This is a solved problem, but it has been solved by companies that charge for their services.
i just googled "typography introductory textbook" and found at list one list of 15.
of those the earliest publishing date was 1999, but if something worthwhile happened in the field of typography before then i suspect it will be reposted in newer books. plus reference to any recent issues in typography.
Are any of those good? Which of them is best? And most interestingly, what list are you looking at, as my Google results are a decent looking Amazon link, an empty Amazon link, a "Personality Quiz", a blog post with a few books, this comment on Hacker News, something on economics, something on typography on the web, et cetera.
Given the results, you could guess that the first link on Amazon might be okay, but this is garbage compared to actual research. At least the random blog post mentions a couple of options, but who is this person, and why is there only one such blog post? This is a really old subject, with lots of material - hiding somewhere.
More importantly, with Google we play keyword bingo. Your search of "typography introductory textbook" returns more authentic results than "typography textbook", which returns publisher links and promotional pages almost exclusively.
And prior to the Internet, the physical limits of information didn't equally determine the types of questions we asked?
It's still true there's have-now and have-laters. This is especially prevalent in technologies. Your smartphone will someday become common in third world countries.