You could make the difference between 'just in case' kind of reading (I could someday use this) and 'just in time' kind of reading (I need to know how this work

You could make the difference between 'just in case' kind of reading (I could someday use this) and 'just in time' kind of reading (I need to know how this works right now). If it belongs to category 1 it is entertainment/waste of time. Else (and if good content) it is actionable, valuable resource.