Reading "older publications" published by the Watchtower is actually encouraged.
Watchtower, 1999/10/1/pg.23
One day in about October 1941, while I was witnessing in the marketplace, someone spoke about a Witness of Jehovah who lived in a nearby town. He was a former policeman named Christos Triantafillou. I went to see him and learned that he had been a Witness since 1932. How happy I was when he provided me with many older Watch Tower publications! These really helped me make spiritual progress.
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Watchtower, 1981/7/1/pg.10
“I accepted a teaching job in Ganta, where my mother lived. She was studying with Jehovah’s Witnesses. In time, I, too, accepted a home Bible study but with the idea of proving to the Witness that he was being misled. After our first discussion, in which he amazed me with answers from the Bible to all my questions, I had to conclude that I was the one who was misled. . . . I decided to read some older Watch Tower publications to see if I could find any contradictions. But this literature only strengthened my faith in the Bible as God’s Word and in the Witnesses as his people.
Petra!