So you're on the bus, heading to your job as a lightbulb filament repairman. On the way, you see a billboard advertising a new book by your absolute favorite author. A quick Smart Phone search reveals his new book stars a lightbulb filament repairman! Wow, your life's work AND your favorite author! This is going to be amazing!
You buy a first edition from the bookstore down the street during your lunch break and that night settle down in your couch and start reading.
...What??? Did the main character just straighten a filament without sterilizing his equipment first? Why didn't he check the make of the lightbulb with any sort of database? Did this author do any research about this career at all??
Well, it turns out he might have, but he's still not going to know more than you do. Unless he's Writing What he Knows, he's just learned enough to tell a story, and story takes precedence over realism. Also, most of his readers (unlike you) know nothing about lightbulb filament repair, and so these errors go unnoticed by them.
This refers to the tendency of dissapointment by people when they read a work about something where they are more qualified about the subject matter than the author. Compare with Dan Browned
, where any audience member can quickly realize what they're reading is false, without insider knowledge.