The old saying that "you can't judge a book by its cover," is simply not true, at least as it applies to actual book choosing. It's untrue not just for the reason you might think. I believe you can judge a bad book by its cover, or at least, you can judge whether or not you will be interested in the book. For example, I never pick up a book that has planets and spaceships on it. I also only infrequently pick up books with women in hoop skirts pressed against shirtless pirates. But you can also think a book will be good because you like the cover, and then find that you've been led astray.
Most recently, this happened to me with a book that had an arresting image on the front and a promise of a mystery in the description on the back. The story itself was a disappointment. So, the premise is about this artist woman from the city who moves to a small town so that she can focus on her writing. She secures this amazing farmhouse with a giant barn. However, shortly after she moves in, she has a terrible migraine and then learns the next day that a local boy (a boy who shoots crows) has gone missing. She's seen the boy before, and in fact confronted him for shooting the birds around her farm, but she has no recollection of what may have happened to him. She vaguely recalls that she saw him on the edge of the woods shortly before his disappearance, but that's it. The story alternates between her growing unsteadiness, prescription drug addiction and isolation and the process of the town detective who is trying to locate the boy or whomever hurt him.
Halfway through, I guessed the secret. Though I like to be right and I also like for the endings to make sense (i.e. not to turn out to have some weird twist you could never anticipate), I don't like for the solution to be too easy. What's your guess? I'll give you another hint--the artist woman can no longer paint and along with popping lots of Vicodin, she also has moments where she recollects the sneering face of her ex-husband. Yes, you are right. She did it. It was an accident though. She was yelling at the boy for killing the birds and she reached for the shotgun and blammo! It went off, killing the little boy. But instead of going to the police, she decided to bury him in the barn and hope for the best. And the reason she was even aggressive toward him is because his jeering face reminded her of her ex-husband. Not enough--- that's not enough of a motive and it also doesn't compute that she would not go to the police and then also not remember any of it. Good cover, flimsy story.