It depends on what you mean specifically by "worth your time"? What "value" (in the sense that you're using) are you trying to get from the book? If you are reading to solve a specific problem, then a book being worth your time would depend on its ability to help explain the problem or approximate ways towards a solution. However, if you are reading non-fiction for other reasons, such as leisure, then the value-approach becomes more complicated.
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It depends on what you mean specifically by "worth your time"? What "value" (in the sense that you're using) are you trying to get from the book? If you are reading to solve a specific problem, then a book being worth your time would depend on its ability to help explain the problem or approximate ways towards a solution. However, if you are reading non-fiction for other reasons, such as leisure, then the value-approach becomes more complicated.