An interesting history of the paperback book, including information regarding “collectable” paperbacks, https://www.ioba.org/standard/2001/12/a-short-history-of-paperbacks/.
As a child growing up in the city of Liverpool, I well remember a glass bookcase full of paperbacks, in my grandfather’s house in Speke (a suburb of Liverpool).
Most Saturdays my Grandfather and I would go into W. H. Smiths and buy a paperback, often by Enid Blyton, https://en.wikipedia.org/wiki/Enid_Blyton.
I lost the majority of my vision at 18-months-old due to a blood clot on the brain. Consequently my grandfather would spend hours reading to me, as I was unable to read print books.
I think of my grandfather whenever I pass by a branch of Smiths. The scent of books and magazines eminating from the store brings the memories flooding back.
Sadly I no longer have the books my grandfather bought for me, Some of which where, no doubt collectable. However, where they still in my possession, I would not part with them as some things possess value which can not be measured in monetary terms.