This is the 12752nd most frequent Korean word.
대화체다
It means "to be conversational in tone."
In this sentence, '대화체다' specifies that the text within the book is written in a conversational style.
이 책은 대화체다, 그래서 읽기가 쉽다.
This book uses the conversational tone, so it is easy to read.
Here, '대화체다' describes the style of the movie's script as conversational.
그 영화의 대본은 대화체다, 현실적이고 자연스러워 보여.
The script of that movie is in conversational style, making it seem realistic and natural.
In this context, '대화체다' is used to explain the typical format of children-targeted books being written in a style that resembles conversation.