My introduction to the way that businesses work was an "Engineering Economics" course. It is about how accounting works, i.e. "financial accounting" vs. "management accounting", the time value of money, what the numbers on a quarterly report mean, &c. If you find a course syllabus online you can see what topics are covered, and a find textbook.
Also when I was seeking this type of knowledge, I read chapters 2,3,4 of http://pmbook.ce.cmu.edu/ , which I found by looking at a MIT opencourseware course on project management. The textbook is about construction but the important aspects transfer to anything.
I think the most important thing is to learn the nuts and bolts. When you get comfortable with all that, then you can start to think at a higher level.
Also when I was seeking this type of knowledge, I read chapters 2,3,4 of http://pmbook.ce.cmu.edu/ , which I found by looking at a MIT opencourseware course on project management. The textbook is about construction but the important aspects transfer to anything.
I think the most important thing is to learn the nuts and bolts. When you get comfortable with all that, then you can start to think at a higher level.