[kipari]

For a more gentle introduction, check out 'The METAFONTbook', also by Donald E. Knuth. I think that it is still not available in a digital format, but your local CS-oriented library might have a physical copy.

[enriquto]

One of my favorite reads! Somehow, it turns out to be much funnier than the TeXBook, which is a bit arid. I love when he explains that drawing a beautiful S is wickedly difficult. And the metafont language is quite slick.

[Tomte]

The character S also has its own chapter in Knuth's "Digital Typography": https://www-cs-faculty.stanford.edu/~knuth/dt.html

The half-tone chapter is also quite cool.

[dhosek]

I remember when the half-tone article was first published in TUGboat. In those days when scanners were exotic equipment not easily accessible, the illustrations were amazing to see (and to recreate).

[guylepage3]

This is very cool. Thanks for sharing.

[daffy]

It can be found with images missing. The full version can be borrowed from archive.org.