I haven't read non-textbooks in a while, so these are just some of my favorite books that have really stuck with me over time:
Ella Minnow Pea by Mark Dunn - very creative, light, fast, and intelligent, and just generally entertaining.
Blood Brothers by Elias Chacour - This is a historical book that helped me be more Christlike and understand a conflict I thought I knew the right side of. It's a great book about compassion and brotherly love, even for those you may see as your enemy.
The Chosen by Chaim Potok - Again, a book that taught me important things about compassion, and helped me broaden my understanding of Judaism a bit more. It was very good.
All The Light We Cannot See by Anthony Doerr - deserves all of the praises it gets. A spectacularly written book.
Racism Without Racists by Eduardo Bonilla-Silva - So good. So informative. So clear. Is this technically a school textbook, but it is a GREAT non-fiction read to help you pinpoint your own invisible biases. Spectacular literature on the problems of "colorblindness."
The Years That Matter Most by Paul Tough - is what I'm reading right now. It's a really interesting, journalistic approach to the impacts and problems with college, admissions, testing, and the struggles of the working poor to gain access to this vital stepping stone of social mobility.
Love Your Enemies by Arthur Brooks - I'm slowly working through this one, but it's really good. I'm trying to learn to be more forgiving, better at listening, and better at engaging in conversation without getting mad at people I disagree with. This book is a great self-help, religious, reflective resource.
The Liberal Soul by Richard Davis - This book is also REALLY good, and helped me understand my own way of thinking about the world as it relates to my religion and politics... but in a way that is educated, nuanced, and appreciative of people who think differently. 100% recommend.
Ender's Game by Orson Scott Card - though certainly, you've read this by now.
The Glass Castle by Jeannette Walls - Man. This one is emotional. It's deep. It's thought-provoking. The movie did a really good job, but you have to read the book and work through your feelings about family, poverty, and the ways people try their best.
The Green Glass Sea by Ellen Klages - Is oriented for youth audiences, but I still remember it as one of my favorite historical fiction novels I have ever read in my life. It's about a girl that lives near the nuclear testing site in Nevada around World War II. Again, deep, symbolic, beautiful.
11/22/63 by Stephen King - Hey, how about Sci-Fi, time travel, and history? This isn't a scary Stephen King novel. It's amazing. Not conspiratorial, but gives you a cool fictional perspective on a significant moment in U.S. history. I was blown away by his authorial capabilities in this book. I stayed up until 4 am reading it when I was almost done.
Okay so at the end of the day it turns out I haven't read much of anything since high school, and when I do read I read "basic" books, so I just really love the classics and popular books. So don't rely on me if you want a list of books that you haven't read before.