I'm going to lay it down simple.



Anything published before 1923 is guaranteed to be in the Public Domain.



Anything published after 1964 is guaranteed to be Copyright protected.



Between those years, there is a grey area. Some of the stuff is still under Copyright protection while some of it is in the Public Domain.



During that time frame, the authors of these published books had to file a Copyright Renewal to the Copyright Office to ensure their works continued getting protection. If they didn't file a renewal, they lost their protection and the works went into the Public Domain. Because of this renewal procedure, a very large majority of the books published in that time have never received renewed protection. Therefore, there are a lot of books out there in the Public Domain.



To find out for sure which is Copyrighted and which isn't, you have to look at the Copyright records and find out if a renewal was filed for that book. Thankfully, Stanford University has compiled a Copyright Renewal Database . It is entirely searchable and the rate of error is less than 1%. Any book not found in the database, is most likely Public Domain.



In the case that the book is Copyrighted, remember that no one but the Copyright holder (i. e. author) has the right to reproduce these items. The only circumstances where it is alright to reproduce a book is if the author gave you direct permission.

