Give Us the Ballot: The Modern Struggle for Voting Rights in America, Ari Berman describes the events which led to the passage of the Voting Rights Act in 1965, its impacts and the countermeasures its opponents took since then to undermine it through the book's publication in 2015.
I hope reading the book will motivate you to make sure you are registered to vote and actually vote in every election and attempt to understand your options in each election. And when you find your options are limited, then act to improve your options.
The book also is a great example of a phenomenon James W. Loewen identified in Lies My Teacher Told Me: Everything Your American History Textbook Got Wrong. Our public schools, for a variety of reasons, teach students that the United States always improves without explaining that people contested all issues, and some people won and others lost and sometimes those who lost won later. So we have this idea that "Civil Rights" happened in the 1960s, and, well, "problem solved."
This view of social change leads to a dangerous complacency, as the forces of regression and counterrevolution, generally supported by an unrestrained oligarchy, are constantly working to undermine progress. Then, upon discovering that their rights and interests have been forfeited, people make some attempt to redress, typically a demonstration, because that's what the public schools and Santa Clausified Martin Luther King celebrations have taught them. People marched, problem solved. Of course, regulatory agencies and legislatures captured by oligarchs don't respond to limited pressure, and the participants in the march despair that the action they took didn't work.
Supporters of white supremacy used poll taxes, literacy tests and violence to prevent black Americans and other racial and ethnic minorities from registering. When the first Voting Rights Act removed these barriers from registration, white supremacists found other ways to prevent those registered from voting or to weaken the effect of their voting. And this game of cat and mouse continued for decades, until the justices appointed by Ronald Reagan and George W Bush to the federal courts and the lawyers they appointed to the Department of Justice stopped defending non-whites' right to an effective vote. Meanwhile, Republican state legislatures and governors and their electoral commissions pressed every opportunity to restrict voters' likely to vote for Democratic candidates, and the Congress of the United States did nothing to strengthen the Voting Rights Act.
Perhaps the coup de grâce was the 2013 Supreme Court ruling in Shelby v Holder, which severely restricted the preclearance requirement which had deterred jurisdictions from actions which would restrict people's voting.
Read this book and get angry. Then find a League of Women's Voters, NAACP, ACLU, Common Cause or similar organization and support it with your money or time.
And shout out to the Georgia Muslim Voter Project!