The old saying, “Don’t judge a book by its cover” is a pretty simple, useful aphorism.
Still, I prefer to judge as many books by the cover as possible – literally and metaphorically.
The basic point of the saying is to be cognizant of the fact that your first impression may be flawed. True and important. But the take-away for me isn’t to stop judging books by the cover, but to get better at cover-judging.
How much time should you spend on something to decide whether it’s worth your time? How many pages deep should you go before making a judgement?
The fewest possible.
Awareness of your error rate in snap judgement is important. But there’s an acceptable error rate, otherwise you’d spend your time doing nothing important because you were so busy trying to dig deep enough to determine if something’s important. Most things aren’t. Most books aren’t worth reading.
If you want to get a lot done, judge more books by the cover. But constantly check and improve your cover-judging skills.