"Oh, dear me, how unspeakably funny and owlishly idiotic and grotesque was that 'plagiarism' farce! As if there was much of anything in any human utterance, oral or written, except plagiarism! The kernel, the soul — let us go further and say the substance, the bulk, the actual and valuable material of all human utterances — is plagiarism. For substantially all ideas are second-hand, consciously and unconsciously drawn from a million outside sources, and daily use by the garnerer with a pride and satisfaction born of the superstition that he originated them; whereas there is not a rag of originality about them anywhere except the little discoloration they get from his mental and moral calibre and his temperament, and which is revealed in characteristics of phrasing. When a great orator makes a great speech you are listening to ten centuries and ten thousand men — but we call it his speech, and really some exceedingly small portion of it is his." - Mark Twain
As Mark Twain said in the quote above, there is no such thing as an original idea. No story or movie or play-write you will ever encounter will really be "original" as people like to say. Each and every one of them are inspired from others. Take Avatar for example. Avatar is literally Pocahontas with a few differences. I provided a link below if you're interested.
We all take ideas from other authors and icons intentionally and not, but that isn't the point. There is a fine line between plagiarism and simply being inspired by an idea that's already been written. This does not mean that you can steal the world of another author and change the characters and even the plot and call it your own. You still stole that world from someone. Key word: stole. That is a form of fanfiction.
Say, for instance, that world had a maze in it and you were absolutely fascinated with the idea with the maze and made your own story, completely different plot, with a maze. That is original.
It's okay to take elements of another story and make them your own. It would be impossible not to have at least one thing in common with another story. Often times, many new books are very closely tied in with a variety of older ones, but they have something that makes them different. Plagiarism is where you blatantly copy another person's work. Such as taking their world, character's, or exact storyline. Plagiarism is a crime. Don't do it.
Overall, know where your ideas are coming from and make sure that you are not stealing from someone else and you'll be okay.