The Triumph of Injustice: How the Rich Dodge Taxes and How to Make Them Pay by Emmanuel Saez and Gabriel Zucman is a truly radical book. It will change the way you think about our tax system, what does and doesn't work and what is and isn't possible in terms of fixing it. While this is a technical subject, their presentation of data, history and analysis is crystal clear and the occasional chart well-chosen. i don't often describe a book as a must-read but this is one.
In addition, you can visit their tax simulator site, taxjusticenow.org, and see how your own package of tax reforms would affect the dynamics of inequality, past and present. Fun! As Saez and Zucman say, there's "a world of possibility" in terms of tax regimes and what such regimes might be able to fund.