Please try not to become a super-villain after you read this book.
This is a followup to his previous book Influence, and I would certainly recommend reading that first. There Cialdini identifies 6 principles of influence (plus a 7th in this book) that can be used to gain peoples assent. Here he describes powerful techniques to maximize the effectiveness of those principles. Some of the things he describes may seem simple or even obvious, like giving people a warm beverage makes them feel warmer towards you, some are downright odd, for example people will give more 'weight' to a subject if you ask them to hold a heavy object while they're talking about it.
But he also goes on to describe conversation and marketing techniques that are used to subtly guide peoples attention to create 'privileged moments' where the 6 principles are at their most effective. And ways to subtly alter peoples self image so they will see your product as more in line with their values. Cialdini closes the book with a detailed discussion of how abuse of these techniques can destroy an organisation, but it's not hard to see his techniques being misused.
It's important to understand both as a marketer and someone who is marketed to.