And I’m sure if one looks hard enough, there are plenty of YouTube videos that can cover any subject you need.
Wish I had that when I went to school.
Back during most my school days, there were a couple of topic specific study books. One popular brand was i.e. Cliff Notes,
another couldd have been “Algebra For Dummies”.
I never liked the subtle insult of being called a ‘Dummy’, though I’m sure the publisher considered it quite clever and amusing.