A story that shows me motivations or stresses characters are under that I might not have considered before. For example murders are committed for serious reasons and to what appears to others to be trivial ones. Yet a good story will take you into the mind of that murderer and show why the trivial reason isn’t trivial to them.
Good, sharp pace with quiet bits in between giving me good background on the setting and characters, knowing said quiet bits are gearing the reader up for the next big scene.
A satisfactory ending, which is not the same as a happy one necessarily. The ending has to be right for the story and the main character. It won’t feel right if the match isn’t there.
Characters I can rally behind (or metaphorically boo for) but either reaction has to be genuine. I don’t want to see the author’s hand making their characters act in a certain way. The characters’ acting has to be realistic for those characters.
I love getting to the end of a story or novel and in a sense wishing neither had ended. Always a sign of a well told tale! Going back over a story/novel and picking up the bits I missed first go around. This is particularly true for a detective novel. I always miss some of the clues on the first read!
I like a happy ending where the hero/heroine has “earned” it. I also like to see villains get their comeuppance but again in a realistic manner. Villains generally are not going to fall apart. They can be caught out.
Every word to count… Funnily enough that doesn’t necessarily mean everything has to be short but that each word is appropriate for the story being told. In P.G. Wodehouse’s stories so often he uses very long sentences (he’d never get away with it now!) but not a word is out of place and indeed especially when Wooster’s narrating the long-windedness is part of (a) the character’s charm and (b) the character’s characteristics!
Positive developments in characters, especially a character that goes on to make something good out of themselves.
I like pinpointing moments of change in a story and watching the drama unfold.
Feeling a slight sense of envy I didn’t write the story/novel I’ve enjoyed is a good sign - and nothing but a compliment to the actual author!