After Googling my head was spinning trying to get a simple answer from all the legalese sites.
I found the basic book copyright was 14 years with one 14 year renewal.
So why, for example, are Hemmingway’s books written in the 1930s still not in the public domain?
The 14 + 14 year copyright term hasn’t been in effect since early in the 19th century. It became 28 + 14 in 1831 and 28 + 28 in 1909. Where did you read something so obsolete, just out of curiosity?
All subsequent copyright legislature grandfathers in all books that would have gone out of copyright under the older term.
Today’s copyright law puts all material produced since January 1, 1923 (and properly renewed back in the day) under copyright for the full 95 year current period. That means that early Hemingway is in the public domain, but his 1923 books will enter the public domain in 2018, his 1924 works in 2019 etc.
A chart of current term length can be found here.
To clarify, anything originally published in the U.S.A. between 1923 and 1963, which was properly copyrighted at the time and properly renewed in the appropriate year, is currently under protection (works published 1964-1989 were automatically renewed and only need to have been published with a copyright notice). Many works published before 1964 were either not properly copyrighted in the first place or not renewed and are thus now public domain (although this can be painful to prove).
Works that were never published, however, may enjoy up to 120 years of protection regardless of date, meaning that an anonymous manuscript from 1886 could still be under copyright. Works originally published in foreign countries have their own set of rules. See the site that Exapno Mapcase links to.
JRB