Excerpted text exchange in which my friend explains Foucault's work:
Me: What's a good entry point into Foucault?
Friend: I recommend a pair of lectures it appears I sent you as an attachment to an email [on] December 3rd of last year...
in general I would say Discipline & Punish is a good entry point
one could say something like, History of Madness is in some ways the most meta though also specific - it’s about the fabrication of Uruk epistemics / “rationality” qua specific form of legibility in opposition to “madness”, & simultaneously as a form of legibility demanded of / imposed on madness at a specific historical point of pathologization & internment
then Birth of the Clinic is about the epistemics of medicine more generally as a reaction of power to plagues, & related mechanisms of spatial immobilization / quarantine / grid-placement / control that turned out to generalize extremely widely
then Order of Things is about the evolution of epistemic discourse on life, language & labor -> biology, linguistics / philology, economics
through the key developmental period of modern states
then Discipline & Punish is about the generalized development & imposition of epistemic procedures / plans for controlling individuals & masses of people in a coordinated / mechanistic / epistemic-y way
(especially modern militaries, prisons, schools, hospitals again)
& how the actual implementation of this contains / is partially subverted by / secondarily creates additional opaque forms of metis wherever it works
& as is usual of metis, what it winds up doing when/where it “works” in this way is not exactly necessarily in accord with the epistemic plan
then History of Sexuality is about epistemics imposed on / related to sexuality / reproduction / the family / population
this is only one perspective on what these things are about, but I think a pretty fair one
My friend notes that this was an on-the-spot explication that involves a fair bit of hand-waving. It might not hold up to close analysis.