Before buying ANY public domain book to use for your projects, make sure that it is 100% IN FACT in the public domain.  This site is not responsible for any damages that may be incurred if you purchase a book that is not in the public domain and then get in trouble for using it.  Make sure you do your due diligence before purchasing ANYTHING.

As a rule, all US books that were published BEFORE 1923 are in the public domain.

Books published between 1923 and 1963 are in the public domain ONLY if the copyright was NOT renewed.

I will post some tutorials later explaining how to learn if the copyright was renewed, so check back later and learn.