Disappointing Thrillers: How could they have been better?

I don't know what it is about thrillers that gets me. Maybe it's the jacket design or the reviews that call it a page turner. (If it is, I'm unaware of it.) Maybe it's that I want to be surprised. No matter what it is that keeps me coming back to thrillers, one thing is constant. I'm always disappointed. Today, I'm going to talk about three thrillers that I've read and where I think that they went wrong. Every one will have spoilers, so readers be warned.

So, first up. "In A Dark, Dark, Wood," by Ruth Ware  was extremely disappointing to me. I am probably a third of the age of the target audience, and yet I still found it to be extremely predictable and dull. The character motivations were childish, the setting was mildly interesting but proved boring, and the plot was hardly there. The main thing that annoyed me about this was that the murders in the story were committed over a romance that had happened when the characters were sixteen, ten years prior. I honestly can't recall a ton about this, but I think I've covered why it didn't thrill me. 

Next up, "You Owe Me A Murder." I've forgotten the author, and, to be honest, I think its better to keep their name out of it. The premise of this is that  there are two girls who, on a plane to England, joke about murdering inconvenient people in their lives. (A mother & a boyfriend.) Then, the boyfriend ends up dead and the main character is blackmailed into killing her mother. Except she's a decent human and doesn't want to do it.
This had an okay premise, but the villain, Nikki, is where it fell through. She was super shallow, and like most people who are murders, clearly not very smart. At the end of the book, when it is revealed that the potential murder victim is not her mother, but the wife of a man she had an affair with (she's seventeen, so....gross.), she jumps in front of a train. Or something. The ending was a cop out. Nikki would have been much more interesting had she felt remorse, or deviated from her unbreakable facade. Instead she was run of the mill and childish.
The third book I'll be discussing is "This Darkness mine" by Mindy Mcginnis. Basically, there's this perfect student named sasha.  She does out of character stuff and decides that the sister who she absorbed in the womb is living inside of her. (As a twin, this weirded me out a LOT.) There's a bunch of irrelevant stuff, and she somehow comes to the conclusion that the sister is in her heart. She has a heart disease, also. Right before she gets a transplant, she cuts out her heart and hands it to her boyfriend. No explanation or anything. This could have been better if it hadn't been written.

Because honestly, gross.
In conclusion, my problem with a lot of these is how immature the main characters were and how little they thought through their decisions. I don't care how much you love your high school boyfriend, you do not get to KILL someone over it. In addition to that, none of them thrilled me. Clearly, the main character will not die, nor will they kill anyone. (Unless it is their character to do so.) If anyone has any better thrillers, feel free to reccomend them!
(This was not a great post. Better content coming soon xx)