If we attend schools , or universities, our courses are a guide to what we may need to read besides text books. If we have interests in certain professions, or skills, then books on building, carpentry, electric, plumbing, cooking, and much more draw our interests.
The hunger for knowledge is a good excuse to read all types of books, and magazines, or to watch educational programs.
A desire to appreciate art forms, or nature, or the horticultural plants on earth can draw us to libraries where books, and texts are available for the many wonderful people of the world.
Raising children, taking care of babies, teens, and young adult siblings in a family setting can draw parents to educational books on many matters.
Books, and knowledge go on, and on presenting information, and computers open doors to tons of knowledge right to our finger tips. Knowledge is fun, and food, for the Gods.
You have a good point. How do we decide what to read, or what to try to see next ? What interests us helps to open the doors to knowledge. God Bless You.