The author was once a top salesperson in a food chemical company and engaged in selling food additives. He was proud of his job because he believed food additives were revolutionary means for our dietary lives.
One day, when he was celebrating his daughter's 3rd birthday and found her enjoying eating pouch-packed meat balls, he completely changed his mind. The meat balls were developed by him and he knew they were not so much "meat balls" but mere chunks of scrap meats and food additives.
He realized he was not only a producer but also one of consumers and he didn't want her daughter to eat his products. He felt as if he were a ”merchant of death.” The next day he resigned the company.
Unlike other warning books about food additives, such as Don't buy them(Katte ha ikenai), this book sheds light on both pros and cons of food additives. He doesn't make a blind assumption that they are evil. The emphasis is placed on information disclosure and our consciousness.
We can understand how food additives are convenient and efficient. However, we are left with many potential costs to our lives. For example, the author raises a risk that some food additives like hydrolyzed protein can destroy children's tastes. In regard to safety to our bodies, he says there may be mixed reactions because the safety standard of the government is based on experiments of single substances.
The author's central question is, as far as I understand, whether convenience and cheap prices really contribute to our happiness.