When you publish a novel, are all the parts of the novel copyrighted as well or only the whole novel? I am asking the question, because the lightsaber were introduced by different other sci-fi novels, and the ideas should have been automatically copyrighted and yet no one chose to take Lucasfilm to court after the release of Star Wars, does that mean that you can only pursue a person or a company if the whole work was infringed upon and not only one part or some parts of it?
The idea of a lightsaber is not subject to copyright. Copyright only covers the representation of it -- in novels, the specific descriptive text. If a novel included a paragraph of description of a lightsaber, and someone in The Empire Strikes Back said the same stuff in a bizarre monologue, that would be copyright infringement. The basic idea of it would perhaps be subject to patent law if there was a solid engineering description of its mechanism of operation, but then George Lucas could have just reinvented the lightsaber via a different (fictional) method of operation that derives nothing of substance from the patented version, and it would be clear of patent issues. The term "lightsaber" is, apparently, subject to trademark but I'm pretty sure a single (useful-sized) word is not enough to qualify as copyrightable material.
In summation, copyright is about expressions of ideas, not the ideas themselves.
source: I deal with issues of copyright licensing a lot, and have worked in a variety of copyright-heavy fields a lot. Long personal experience with matters of copyright has exposed me to a lot of its quirks.
Everything that is copyrightable is protected by copyright. The expression of an idea is protected by copyright. The author holds copyright to the "bulk" of the publication (the text), but the publisher holds copyright to the design (artistic layout of the text and cover art). If you literally publish your own book, then you are the entire copyright owner.
A lightsaber is not subject to copyright protection – that's metaphorical talk. The name "lightsaber" is subject to trademark protection (also, "Jedi"), because those are protected trademarks, and like Lightsaber Academy you can be sued for promoting unauthorized classes, certificates about lightsabers. It's not that you can't use the words Jedi and lightsaber, it's that you can't "compete" with Lucasfilms using these same terms. The underlying idea of an energy weapon is old news and if ideas were subject to coyright protection, that copyright would have long since expired. Designs (cover art, props in films) are protected by copyright. A word is not subject to copyright protection. A phrase might be, but "X, I am your faaawther" is easily defensible as fair use.
You can't learn much about what is not protected by copyright by looking for cases where the copyright holder didn't file an infringement lawsuit. Sometimes it's just not worth the trouble, sometimes people don't know that they can sue.