Just because a book was printed in 1970, don’t assume that the author is deceased.
Living authors have a right to give or deny permission for the use of their work. Their estates have similar rights for a period after death (fifty years in many countries).
Authors of short runs, less than five hundred copies, often have books left to sell. If someone puts the work up on a free site on the internet, sales drop to zero.
Historical Societies and Genealogical Societies are particularly vulnerable. Until recently, niche publications have been a major source of revenue for many such groups. In most countries, the work is copyrighted for at least fifty years from date of publication, but these books get posted on the internet and the law is ignored.
If someone took your car from your driveway and used it to ferry friends around, no one would argue that it was theft. When revenue is taken from historical societies without their consent, it is described as “sharing”. This must stop.
Writing is not a lucrative profession. Authors need to sell their remaining publications. Historical Societies and Genealogical Societies also need the revenue from their works.
Ask permission before re-publishing a book on the ‘net.