Public Domain
A public domain book is a work no longer protected by intellectual property laws, usually because its copyright has expired, allowing anyone to freely print, distribute, adapt, or sell it without paying royalties or seeking permission.
In the U.S., most works published before 1929 are in the public domain.
In the U.S., a copyright for created works lasts 95 years from publication or 120 years from creation, or enters the public domain 70 years after the author's death.