Have you ever started reading a book, excited by the premise, and then slowly ran out of steam? Around page 50 or so you realize that you don’t particularly care what happens next, the characters haven’t grabbed you, the plot, as convoluted and intricate as it might be doesn’t interest you, and so, with a shrug, you set the book down and pick up another? 

And yet with other novels you can be grabbed from page 1, instantly riveted so that you read the whole novel in one night, unable to put the book down, turning the pages as fast as you can till you hit the end and look up blinking to see that it’s past three in the morning?
What is it that makes the second book so compelling and the second as flat as a week-old Coke? 
It’s not plot. It’s not the amount of explosions or chase scenes. It’s not pacing, though that can amp up the compelling factor. I think it’s a combination of authorial voice and caring about the characters. Whether they’re SEAL commandos or high school vampires, whether they’re professors in the twilight of their careers or blue skinned aliens, you have to really care about them. About their fates. About what is going to happen to them, whether they will be hurt and crushed or find a way to win through against the odds. Once you have a reader invested in your character, well, you’ve got them.
So this leads us to the million dollar question: how do you get your readers to care about your characters? 
Before I take a stab at answering that question, I want to hear from you guys. What have the characters you’ve cared the most about shared in common? What was it about them that made you care about their fates, that made you turn the page?