I'll add three more (although I have lots of books that have influenced me after 60+ years of reading

).
First,
It Can't Happen Here by Sinclair Lewis. I first read this book in the early 1960s and thought, it really can't happen here in the United States. Then came Richard Nixon and Watergate and I realized that it can happen here if we are not diligent about protecting ourselves from the extremists on both the left and the right. This caused me to subscribe to newspapers and magazines with divergent viewpoints so that I always have more than a single viewpoint on an issue, which has led me to choose causes more knowledgeably (or so I hope).
Second is the trilogy I am currently reading. Written by Taylor Branch, the trilogy begins with
Parting the Waters, and is followed by
Pillar of Fire and
At Canaan's Edge. It is the story of the times of the Civil Rights Movement in the United States centering around Martin Luther King, Jr. It is not his biography per se; it is more a biography of the years 1953 to 1968. This trilogy -- which is available in ebook format (I bought my copy from the Sony bookstore), each volume separately -- shattered several perceptions I had about those times. Perhaps the biggest change for me was the shattering of the belief that President John Kennedy and his brother Robert Kennedy, the US Attorney General, were pro civil rights and actively worked to advance those rights. The second shattered belief was in regards to the unity of the civil rights movement leadership as to purpose and tactics. If I had known then what I know now about Roy Wilkins and the NAACP as a result of this trilogy, I would have had a much different view of the NAACP, and it would not have been a postive one.
This trilogy has shattered several other beliefs I had about the era, and I expect more will be shattered as I complete the second and third volumes.
One final book, at least for this message

, would be Doris Kearns Goodwin's
Team of Rivals, also available from the Sony bookstore so probably available in other formats. This book increased my already high esteem for Abraham Lincoln and his abilities. But more importantly, it made me wonder why modern-day presidents are so incapable of emulating Lincoln's footsteps in regards to assembling a cabinet that is in the best interests of the US as a country. One of Lincoln's cabinet members was a rival for the party nomination, something not done today for fear of giving a rival a platform. It changed the qualities I look for in a candidate and made me focus on more than the news soundbite when deciding who to vote for.