I can always tell if a book I’m reading is going to be a keeper or not by how involved I get with the characters.
If I start screaming inside my head for a character to not be such a stupid idiot and not make such a bad choice…yeah that’s probably a sign I care a little bit about the character. And, as long as the choice, stupid or not, whether I agree with it or not, fits with the character’s values and beliefs as we’ve seen them to-date in the book, then I’ll keep reading. Because I have to know if the character comes out the other side okay or not.
But if that choice seems off for that character, then I’m done.
What about you? How can you tell if you’re deeply invested in a book?