On one hand, it's amazing that these treasures have survived.
On the other hand, it's alarming that they only survived by luck. I know a second hand book dealer, who got asked to come over & value a deceased collection. The previous owner was known for buying up all sorts of rare sci-fi & fantasy books from the 50s & 60s, so there was much interest. When the guy I know got there, it turned out he'd put them all in cardboard boxes in an outside shed, on a property outside the city. Between a leaky roof and rodents, pretty much everything was ruined. They did salvage some lightly water & mould damaged first edition Lensmen novels (amongst other things) from near the centre of the piles, plus some other stuff, but the cost of restoration/stabilisation was going to eat most of the potential sale price.