I've recently read Peter Schweizer's book, Extortion: How Politicians Extract Your Money, Buy Votes, and Line Their Own Pockets. The book offers a solid account of the way politicians use their political power to extract money from interest groups for the benefit of the Permanent Political Class.
Interest group activity is often viewed as bribery: interests offering campaign contributions and other benefits to legislators to get legislators to pass legislation those groups favor. Schweizer argues that the reality is the opposite: legislators hold out on putting legislation up to a vote unless interest groups who support it pay up; or worse, legislators threatening to pass legislation that will harm those interests, unless they pay the legislators to kill the legislation.
Payment typically comes in the form of "contributions" to campaign coffers, and Schweizer explains in detail how legislators are able to convert funds for their personal benefit, using lots of real-world examples. In addition to personal consumption, legislators can hire friends and relatives, and can extort firms to hire their friends and relatives.
The book explains how the legislative process really works. It is the antidote to what is typically taught in public school civics classes. The book offers numerous examples, and is well-documented and footnoted. Every American should read this book.