When I first became involved with the writing community, one thing I heard a couple times that stuck with me was that your details should be accurate when you're writing. Whether you're writing historical non-fiction or a fantasy novel set on a different planet, it is important that you get anything "real" correct, such as elements of the setting. People will notice if you get things wrong, no matter how minor you might think that specific thing.
For example, if you're writing a book set in Colorado Springs, you research wildlife before you mention seeing a grizzly bear in your book. We don't have grizzlies. We have other types of bears. People who live here will notice, as will others who have been here, or who study grizzlies, or who have any interest in wildlife in the west, so on and so forth. There will always be someone who notices.
People want to get lost in a book or movie, but when some minute detail catches their attention for being inaccurate, it can drag them out of it and ruin the experience. Even if the writing is phenomenal, something minor can rip a person right out of the story. Consider something like a cell phone being pulled out in a movie set in the 50's. That's an extreme sort of example, but would it catch your attention? Would it remove you from that suspension of disbelief that caused you to be absorbed in the story being told? Almost certainly! In fact, if you look at IMDB.com, many of the films have a section dedicated to goofs people noticed.
It doesn't take long to look up little things like native wildlife, local weather, state/city government, etc. Technology has even made it possible to see a street corner or storefront via satellite. You just have to go on the internet and you can see an entire neighborhood, zooming around to look at the houses, the lawns, the types of trees.
Historical novels are trickier, of course, but if you go into historical fiction or non-fiction, you likely go in fully prepared to do the research. One of the examples I first heard was from local author M.J. Brett, who taught before she became a writer. Her class was reading a novel that was set back during WWII, and a local area was detailed. This book had a couple driving through a part of town that would have been rubble on the day they went through it, thanks to bombing. These kids caught it and ridiculed the book; it ruined the entire story for them, made it so they couldn't take the rest of it seriously. Such a small detail, though probably not the easiest thing to find.
I'm not saying it's easy to do this research, but it is important. If you find yourself questioning something, it's best to look it up. Chances are, if it strikes you as wrong, someone else will respond in the same way.
By the way, I looked up London bombings in WWII to be sure I was talking about the right time frame (wouldn't THAT be embarrassing, considering the topic), and there are old newsreels of the bombings, which was interesting, so I thought I'd pass one along: NEWS REEL.
Is there a book or movie that has been ruined for you due to a botched detail?
May you find your Muse.