Paul Rubin wrote:

The other thing is that while only around 15% of copyrights were
renewed, there's not a reliable way to tell whether a copyright was
renewed or not (there's a Library of Congress database but it's
inaccurate). So you could find a book from 1930, notice that it's not
in the database, republish it, and then some dork claiming (truthfully
or otherwise) some connection with the original publisher says he's
the copyright owner and he renewed the copyright in 1958 and that he
is going to sue your ass if you don't pay up (but of course you don't
get to see the renewal documentation unless there's an actual
lawsuit).

Thank you so much for your lengthy and detailed reply.

Now, I have another question.

Suppose that the great-grandson of the guy who wrote the book in 1932
shows up and claims the rights to the book I have reprinted.

Is it correct to say that at the worst all I owe him is a royalty, say
10%, on the books I have sold and, since I have not sold any of these
books yet, I owe him nothing.

Regarding the 1937 book, that was by a Soviet author, and since the
Soviet Union did not recognize our copyrights, under no circumstances
would I ever own him anything, even if he were alive today. (He died in
1942).

Sam Sloan