It is important that authors are aware of the aspects of copyright law that might impact them the most, both with respect to protecting their own books and creations and to avoiding infringing on another's copyright.
Let's take a look at some of main aspects of copyright law as it relates to authors and their works.
Copyrighting is automatic—but courts will require official registration.
Your ownership over your own intellectual property is yours simply by having having created it. Copyright protection is extended to any work of "original authorship" (i.e., something creative enough to have an actual author; not simply a word or phrase) that has been "fixed in a tangible medium" (i.e., your computer or notebook).
However, simply owning a copyright is not, in practice, always enough. In order to bring legal action against someone for selling your work without your authorization, for example, the courts would require you to have an official copyright registration on file. (You can certainly do this after the fact, but your case is much stronger when you've held a copyright registration before the alleged infringement took place, and the Copyright Office provides certain incentives to encourage registration.)
In addition to legal proof of ownership, there's another excellent reason to register your copyright: it creates a publicly searchable record of your copyright registration, which is an excellent idea for anyone who would like to make money off of their creative works. For example, if someone read your book and wanted to produce a movie based on it, they would need to ask your permission first. Allowing yourself to be searched in the Copyright Office provides anyone potentially trying to get ahold of you a central place where you can be found. This is just good business!
Copyrighting protects words, not ideas.
Remember the J.K. Rowling controversy, where the author was accused of infringing on the rights of another author whose books portrayed child wizards? Or the similar controversy surrounding Dan Brown and his best-selling Da Vinci Code?
In both of these cases, the authors in question were held not to have infringed on any copyrights, even though the claim that the works were more than casually similar were in fact quite true.
How were these authors able to escape prosecution? The simply fact is that ideas are not eligible for copyright protection. Works of original authorship are. I can write as many books about child wizards, white whales, circles of hell, or distant alien planets that I wish—no one author enjoys exclusive rights to an idea.
Derivative works require the permission of the copyright owner.
While it's true that ideas are not protected by copyright restrictions, I will certainly get into legal trouble if I create my book using Ms. Rowling's original characters. Sequels like this (along with any other new creative work that incorporates elements of an already existing work) must be created or authorized by the original copyright holder; in other words, the author must give permission for any sequels.
Derivatite works are not limited to just book sequels. There are many other ways a book may result in a derivative work:
Before using the copyrighted material in any way, either make quite sure that your use is covered under fair use laws, or ask the author for permission before you potential infringe on his or her copyright.
A copyright notice is not required.
Copyright law first entered the book publishing world in the early 1700s, and it has undergone many revisions and changes since that time. While a copyright notice (the C with the circle around it, along with the year the book obtained copyright registration and the phrase "All rights reserved") was a requirement in recent decades, currently it is not. Because copyright is automatic simply by having created and recorded a creative work, a book is not required to display a copyright notice in order to be protected under copyright law.
Of course, a copyright notice is somewhat like a "No Trespassing" sign. While it doesn't physically restrict someone from access, it does send a clear signal as to the seriousness of your request. A landowner who deliberately places a sign on the property to warn people away is one that could be expected to follow up on the warning; an author who stamps a copyright warning on the book for all to see is one that appears not to tolerate unauthorized use to her book.