As a reader, a writer, and an agent, I read thousands of stories a year—or at least the opening pages of thousands of stories. And, all other things being equal, the reason I most often stop reading is a lack of narrative thrust.
Narrative thrust is the taut building of story, beat by beat, scene by scene, chapter by chapter, using the complexities of plot and character to propel the story forward in a dramatic arc that peaks at the climax. You must write each scene so that it leads logically to the next, as if you were connecting a model train, car by car, presenting story questions as you proceed down the track, pushing the action forward to its inevitable, if unpredictable, ending.
The Big Reason Why Agents and Editors Often Stop Reading