"The best subjects are always people, who never fail to amaze me by their unpredictability"

In this quote, Ronnie James Dio, a famous musician, is revealing his belief that the most interesting and fascinating topics to study are people. He explains that he is constantly impressed by the unpredictable nature of humans. This could refer to the fact that individuals are complex and multi-faceted, making them tough to completely comprehend and constantly keeping us on our toes. It could also recommend that people have the capability to shock us with their actions and behaviors, making them constantly interesting. Overall, Dio is stressing the importance of studying and learning from people, as they are a relentless source of wonder and intrigue.