Sometimes the small things irritate me in a book. I'm talking very unimportant details here, things that other people may not notice. But if you're incorrect about something that I'm passionate about you're going to annoy me.
I only have on example for this right now. And I should mention only because I'm reading this book and it's annoying me EVERY TIME it's mentioned. In Stieg Larsson's bestseller The Girl Who Kicked the Hornets's Nest there is a character named Monica Figuerola.
Part of Monica's background is that she's described as 6'4" (listening to audiobook so I can't confirm this exactly but she's over 6 ft) and as a former elite gymnast.
As someone who competed in very low level gymnastics but has followed the sport (and cheesy movies/television shows about the sport) this stops me in my tracks EVERY TIME IT'S MENTIONED. Why you ask?
Elite gymnasts are not that tall. In fact Sveltana Khornia is the tallest elite gymnast that I've ever heard of t 5'5". And she looks like a GIANT compared to most gymnasts. On some events she was beautiful, especially the uneven bars where her long lines were very graceful. But in other events her legs and heigh seemed to be a hindrance and kinda awkward.
So a gymnast "who almost made the Swedish Olympic team" and is over 6ft is not believable. I know Sweden is not a gymnastics power (USA, China, Russia, Romania, etc) but it's just ridiculous. Larsson wanted her to be a gymnast to explain her athletic build, muscles and I think to add a bit of sex appeal but for me its disruptive and doesn't work. The book never even mentions that her height is unusual for the sport which makes me think Larsson knows very little about gymnastics.
I'd say over 90% of readers don't notice. But anyone who knows anything about competitive gymnastics will. Luckily this is the 3rd book and not the 1st. Honestly in the 1st book it may have irritated me enough to prevent me from continuing the series. Just something to think about when you're adding what you think of as "insignificant" details to the story--what doesn't matter to you might bother someone else.