I think nearly all of us have been in a position where we're behind on reading a class textbook and it's the night before a test.
There's no way you can read five chapters in 12 hours, but since half the test comes from the textbook you need to at least look at it. What do you do?
You do this! Most textbooks have their chapters set up in this way: headings, highlighted terms, "info boxes" and maybe a chapter summary at the end. What you do is write down the heading for each section, then copy the highlighted terms (with definitions). Then read the info boxes and the chapter summary.
You won't get a complete
reading done, so you may miss some things, but at least you'll have a better idea of what's in each chapter than you did before!