Originally Posted by Iznogood
As far as I can tell, this is the Carolyn Wells that died in 1942. The book is not listed as "hers" on her wikipedia page, but I guess it's her. So the book became public domain this year from what I can understand
Works come out of copyright on January 1st of the seventy-first full year after the author's death. That is, all deaths are counted as happening (for copyright purposes) at the end of December 31st in the year they occurred.
In life+70 countries, if an author died on 31st December 2000, their works come out of copyright on 1st January 2071. If an author died on 1st January 2001, their works come out of copyright on 1st January 2072.