I suggest that every household buy an EMT basics book or it may be called fire service emergency care. Any kind of book meant for teaching the EMT. You can look on e-bay or used book store, or a college to find them. It won't matter too much if it is a little older, although they constantly change their ideas of how CPR should be administered. Most of it is basic procedures.

It has the basics of how to care for the injured and save lives in an emergency situation.

Others may want to take further steps in the medical area to learn how to suture etc., but for everyone else it should be required reading so that everyone in a group knows the basics of how to care for anyone injured, not just the designated medic. There are parts of it that you may not need to know, but you can skip those parts.(like legal issues) I doubt anyone will be thinking about legal issues when SHTF.