I had a roommate once who had never read any SF before we moved in together. She saw my collection of science fiction and decided to give it a try.
She grabbed a book off my shelf at random—a far future, hard scifi title. Pretty advanced for her first exposure to the genre. She found it very frustrating.
She had no problem getting into the characters or the plot. She understood the science well enough and enjoyed how the author extrapolated it. She didn’t get too tripped up over the genre-specific vocabulary, either, although she did have to ask me what some of the acronyms stood for.
The problem was the setting. She couldn’t make sense of the world of the story, the environment. She didn’t know what things were and couldn’t picture them. Presented with an imagined far-future, alien setting, she felt lost and disoriented.
She was frustrated because she thought she was supposed to understand it. She felt like she was missing something, some key that would bring the world of the story into focus. Something to make it all make sense.