What are yours Best have thing(s) that you, as a reader, want in a book?

Being it fantasy or sci-fi ones.
Is it world building, level of details of characters/things/places, the story itself, how you can relate to a (main) character, other?!

And if possible, why?

For me it tends to be the story itself, of course I can relate to a character, or to the incredible details of a place somewhere. But generally speaking, i’m more intrigued to know the context and the plots of the story the author wanted to give me.

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