This is the 15604th most frequent Korean word.
보던
"보던" means "that was seeing" or "used to see," referring to an action of seeing or watching in the past.
Here, "보던" modifies the noun "책," suggesting that he was repeatedly engaging in reading this book in the past.
그가 계속 보던 책은 정말 흥미로워 보였습니다.
The book he kept reading seemed really interesting.
In this context, "보던" describes the television programs, implying that we previously had the habit of watching them.
우리는 어렸을 때 자주 보던 텔레비전 프로그램에 대해 이야기했습니다.
We talked about the television programs we used to watch often when we were little.
In this sentence, "보던" is used as an adjective indicating the act of watching that was occurring in the past.