A lot of people like structure, and that's what I think this book provides (to some extent).
Sure, you could go to TV/podcasts/movies/anime etc, but, with the exception of maybe a few podcasts, is there going to be much in terms of scripts and the like? This is natural Japanese conversation with a full script! It let's you look up vocab/grammar and listen to native Japanese speakers. And if you follow it's advice, begin to speak in the same way as native speakers. I really can't think of anything that could do more for you.
Also, I've had my native speaker friends tell me multiple times that dialogues from movies/anime/tv shows (drama type shows) are not the most natural Japanese at all... so I don't know how good it would be to use those solely to learn how to speak.
Sure, you could go to TV/podcasts/movies/anime etc, but, with the exception of maybe a few podcasts, is there going to be much in terms of scripts and the like? This is natural Japanese conversation with a full script! It let's you look up vocab/grammar and listen to native Japanese speakers. And if you follow it's advice, begin to speak in the same way as native speakers. I really can't think of anything that could do more for you.
Also, I've had my native speaker friends tell me multiple times that dialogues from movies/anime/tv shows (drama type shows) are not the most natural Japanese at all... so I don't know how good it would be to use those solely to learn how to speak.