After I finished reading The Lake by Banana Yoshimoto, I wanted to know more about the Aum Shinkrikyo cult who in 1995 carried out a sarin attack on the Tokyo underground. I wanted to know why they did that. There is a book online that provides a lot of background, and it is fascinating but very grim. This cult had planned to spray sarin over Tokyo. They had enough precursor material to poison 4 million people. They had a working production facility as well, only not at the required scale, and they had managed to smuggle a helicopter from Russia.

https://academic.oup.com/british-academy-scholarship-online/book/44964