Orphan works are a HUGE problem:
https://en.wikipedia.org/wiki/Orphan_works
Legally, it is a huge minefield.... and there are many works which are currently lost in the abyss.
Nobody knows who the copyright owners are, no one knows if the copyrights were renewed or not, you cannot find the copyright owner, so you do not know who to pay royalties to or even ASK. No one can legally be certain if the work is in the Public Domain or not.
To be safe, most publishers (and boards such as MobileRead) have to err on the extreme side of caution, and strictly enforce the rules on such works (Life+70 in most cases).
SOME publishers (such as the one that reprinted this 1948 edition without knowing who the copyright owner is) will print the work anyway and take their chances. They have the potential to be charged huge fines if a copyright owner comes forward.