In some cases it is reported that books of a questionable nature have been put in the Theocratic Ministry School library. It would not be appropriate to include fictional material, Bible commentaries that highlight higher criticism, or books on philosophy or spiritism.
Except that I still suspect that the WTS has a special "for research only by approved persons" library in NY Bethel that has exactly this kind of literature. (they did when I was there in the 1970s at least) Not to mention whatever library references they needed into the UN for...
I don't think that the idea of cleaning out "old literature" has ever been put in print, but it certainly has been encouraged by certain people in leadership from time to time - it is a common JW trait to avoid older WTS writings.