well when you think about it all book ideas came from some other book Idea I mean if you look at all vampire books the idea of a vampire wasn't really there's. They "stole" the idea of vampires from someone else. this can also link with plot ideas, there are the good guys and bad guys, type of plot development that has been used soooo many times. There's a few better examples I can think of i just cant be bothered posting them lol) so actually everyone has stolen ideas from other books

of course if it was basically the same book and it stole the books plot development, morales and theme's ect. I would understand, I hate Authors who do that, it shows a lack of self thought and imagination.