Copyright is a property right. It means that someone owns the right to make copies of a book, in the same way that a person owns a shirt. One of the little known things about copyright laws is that, unlike owning a shirt, there is a time limit. In Hong Kong copyright lasts for the life of the author, plus fifty years. Afterwards the book is in the public domain. (HK Copyright Ordinance Section 17.2) (Note: This is Hong Kong law, other countries may have different time limits.)
The public domain is very important; it is the whole cultural inheritance that all of us own. If we compare it to a city, the buildings are the copyrighted books. The streets and parks are the public domain. We need the streets to get to the buildings; we need public domain material to write new copyrighted books. Good books build on the culture that went before them, but don't just make copies.
What can you do with public domain books? Anything you want. You can print them and sell them. You can make a movie based on them and claim your own copyright on your new creation. It is often pointed out that public domain books are free as in speech, but not free as in lunch! You are free to use the text. However you must pay for the internet access to download it. You pay for paper and ink to print it. But nobody can stop you from using it or charge you a fee for the text.
Copyrights expire at the end of the year. So on the first of January, 2014 all the books, computer programs, poems, paintings, songs and so on created by people who died in 1963 will come into the public domain. Aldous Huxley was famous for writing books such as Brave New World. C.S. Lewis wrote the Narnia series. Both of them died in 1963. The poet Robert Frost, the mathematician Jacques Hadamard, the musician Patsy Cline, the poet Tristan Tzara, the anthropologist Melville Herskovits and the painter Georges Braque all died in 1963.
If someone owns a painting by Georges Braque they still keep the physical painting. Copyright only covers intellectual property, not touchable things. However anyone can make copies, if they have a photograph of it. If you borrow a copy of Brave New World from the library you can copy the text. However you cannot copy pictures that might have been added to a more recent edition. (The actual typographical layout is protected from photocopying for 25 years.)
If you have a CD with songs by Patsy Cline, you can freely make a copy, but you must pay for the blank CD. If you make a movie with Patsy Cline songs, a story by C.S. Lewis and a cubist background by George Braque you will own the copyright on this new creation. That new copyright will last for your lifetime, plus fifty years. So the more recently made Narina movies are still under copyright, but you are free to create competing versions. However you must wait until the first of January 2014, until then all these materials are still under copyright.
Disclaimer: I am not a lawyer and this article is not formal legal advice. It is based on my reading of the HK Copyright Ordinance and Dr. Alice Lee's Intellectual Property in Hong Kong. No guarantee whatsoever is made that the text is legally accurate. Laws can be changed and may have been modified or overturned after this article was written.