Consider the stories you've read.
You can set familiar folks in a familiar setting. Maybe you've never been in an English Lord's library, but it's not much different than some rooms you've been in. Maybe you've never known a spinster who sorts out how the body got in the library, but she's not that different from some spinsters you've known.
You can set familiar folks in an alien setting. You may not know an astronaut like Buck Rogers, but he's not too different than other guys you know who drive airplanes. But there's no way you know about the alien wonders of the 25th Century.
You can set an alien in a familiar setting. You may not know anything about that E. T. who just got stranded by a visiting UFO. But drop him in a suburban neighborhood with kids riding bikes and just enough electronics to Phone Home.
What you cannot do is put E. T. in the 25th Century.
The reader of any story needs touch points s/he can relate to. And even when the reader follows Buck Rogers into the 25th century, s/he can grok Wilma Dearing's attractiveness to Captain Rogers. And even more alien evil Princess Ardala just happens to be smoking hot.
Every male and some of females feel the attraction of a beautiful woman. Readers need to relate to your story at every point. The way in which the reader relates the familiar can be less interesting than the alien. Space princesses are alien because they are from space, but they're familiar because they're still princesses.
The reader has only a finite capacity for handling the alien. You cannot put the alien in the alien, because it overwhelms this capacity. So, you have to manage the balance of the familiarity and alienness you present to the reader. Too familiar, and you risk the story being boring. Too alien, and you risk the story being incomprehensible.
Remember the two primary principles of prose: You must be clear, and you must be interesting. This should guide you in deciding how much familiar and how much alien belongs in your writing.