I don’t know much about antique books, except for the out of print reference books that I use for my hobbies.
The one thing I will say is that it’s sometimes hard to pinpoint values in the collectables market. If the $40,000 price tag for the mint state 1939, signed first edition came from an auction, it could be an outlier. If two collectors go nuts in an auction they can bid each other to ridiculous levels that won’t be duplicated for a long time if ever. I did that to myself once, and I hope I never do it again.
Later editions of the same thing usually are not worth nearly as much.
The example I can point to is the Washington Before Boston medal that was awarded to George Washington by the Continental Congress months BEFORE the signing of the Declaration of the Independence was signed in 1776. Congress voted to metal to Washington after he placed guns above Dorchester Heights which forced the British to leave Boston Harbor. This was at the very beginning of the war, and was more of a symbolic victory than a major one. The war would continue for another six years.
Washington would get his medal in 1789. The medal awarded to Washington was in gold. It is now held by the Boston Public Library. Others were made in silver and copper.
Those other medals, in copper, that were made with THE SAME SET OF DIES are worth perhaps $10,000 to $12,000 or more in the top conditions. Later examples have been made over the years from different dies. There have been at least six different issues of the medal. The very latest ones are worth about $40 to $50. The design is the same, and in some cases it takes a expert to tell the difference, but as you can see the values can vary a lot, depending on when the item was made.
The bottom line is that the later editions are often worth less, sometimes a lot less.