public domain

That being said, public domain is a term applying to copyright statute, referring to a work whose copyright has expired and passes into public ownership. The tales of Mark Twain and earlier works of Sir Arthur Conan Doyle and Edgar Rice Burroughs, the King James Bible, The Three Musketeers, The Swiss Family Robinson, Shakespeare's plays, and many others are examples of public domain literature. They may be reprinted and resold by others, translated, used as the basis for new books or movies, or have other derivative works created from them. Project Gutenberg and Wiretap have archived many public domain works electronically.

In the United States, most books published before 1923 are now in the public domain. Sadly, it will be years before any books from later time periods enter the public domain, thanks to recent changes in copyright law. Corporate concerns such as Walt Disney and descendants of long-dead authors and artists have gradually eroded the "limited time" clause of copyrights as stated in the United States Constitution from its original twenty-eight years to life of author plus seventy-five...which means that there is little probability that even a work created in your grandparents' generation will pass into the public domain while you are still alive.

Additionally, Rose Thorn noted that in the UK, the Crown retains copyright to government works.

I will freely use his facts and ideas, because facts and ideas are not covered by copyright.

Everything first published before January 1, 1923 is in the public domain.

Almost everything published before January 1, 1964 is in the public domain. The only publications in this category still under copyright are those for which a copyright form was filled out and submitted, AND a copyright extension form was filled out and submitted 28 years later. It is estimated that roughly 85% of all works published between 1923 and 1963 are in the public domain. The percentage varies greatly by the type of work.

The records of copyright extension forms are in bad shape. It is nearly impossible to tell, for certain, if a particular book from this period is still under copyright.

Here is a table for things registered with the Copyright Office in 1931-32 and not renewed in 1958-59. Note that there are many many things created and published in 1931-32 that were never registered and never had any copyright protection.

I am copying this table from the book Public Domain, which itself is copyrighted. I can use it, though, through either of two loopholes. The first is Fair Use. I'm using only a very small excerpt and stating my source. The second is that Mr. Fishman got this data from the Copyright Office, and therefore was produced by the Federal Government, and therefore was already in the public domain when he used it.

Type of Work         Allowed to Expire
Books                    93%
Periodicals              89%
Lectures, speeches,
sermons and other works 
for oral delivery        99.6%
Drama                    89%
Music                    65%
Maps                     52%
Works of Art             96%
Technical Drawings       99.6%
Art Prints               96%
Movies                   26%