This Week's Topic: What Makes Readers Invested In a Story?
Short answer: Empathy.
Longer answer: Giving a damn about the character(s). A whole host of style flaws or storytelling glitches will be overlooked if the reader cares about the cast. It's not to say a reader has to see themselves in the character. Heck, some readers don't want that at all. OTOH, others absolutely crave self-insertion. Your protag can be the most despicable antihero ever, but if you can make the readers care whether that character lives, dies, suffers, fails, succeeds, or gets a comeuppance, then the reader is invested. They're turning pages. They're putting that book down long enough to pee and coming back. Sure, vivid settings are good. Unique magic or hard science is a nice-to-have vehicle of conflict or development. But EOD, it's all about the characters.
Don't get me wrong. The character(s) don't have to be human or humanoid. Some of my favorite thrillers place the house as the protagonist. Every time a nail goes into a wall, I feel that stab wound. Furniture being dragged across the floor, gouging the hardwood? Wall demolished? Abandoned by the family it cosseted? All the agh, grr, and noooooos.
Want to keep a reader...reading? Give them a character to care about.