There's an interesting wrinkle on the comics side of things. It was eventually deemed not worth the effort to strip covers from comics and other magazines and ship them, leading to the introduction of "affidavit returns" -- in which the distributors simply told publishers how many they and their accounts didn't sell on notarized forms. The problem was that magazine distribution was heavily mobbed up for decades. (Back in the 1950s, a large part of the infamous Senate hearings on comics and juvenile delinquency involved a crimebuster senator/presidential candidate trying to connect distributors to organized crime.) They'd not ship many of the books they'd gotten, lie about returns and and claim the credit for them. Then they'd sell them off to jobbers to resell.
So quite frequently you would find comics that had been reported destroyed being repackaged and sold intact (to go along with the coverless copies a lot of stores sold anyway after they'd stripped them). One day in the 1980s, the guy who owns Mile High Comics found an abandoned warehouse with 11 million Marvels from the 1960s in perfect condition. Marvel said since they didn't officially "exist," he was welcome to them!
I would suspect since those distributors also sold paperbacks, there may be similar treasure troves out there with regard to novels. (I tend to focus more on comics history myself -- I run a site called Comichron in my spare time.)
So quite frequently you would find comics that had been reported destroyed being repackaged and sold intact (to go along with the coverless copies a lot of stores sold anyway after they'd stripped them). One day in the 1980s, the guy who owns Mile High Comics found an abandoned warehouse with 11 million Marvels from the 1960s in perfect condition. Marvel said since they didn't officially "exist," he was welcome to them!
I would suspect since those distributors also sold paperbacks, there may be similar treasure troves out there with regard to novels. (I tend to focus more on comics history myself -- I run a site called Comichron in my spare time.)