I would recommend everyone to make sure they read at least the following 4 books in their 20s.
The first one is Joseph Heller's 'Catch 22.' This book exposes the absurdity of war. From the soldier's point of view, there was no good and bad side, no moral heroes in the Second World War. There was just absurdity, greed and horror. People, cities, countries, and ordinary soldiers too were the toys of people who were vying for power and influence, and doing so for unjustifiable reasons. The book exposes the nature of power and what it is like to live in times of a catastrophy. It helps one to always be vigilant and suspicious of politicians, and to see through the lies of 'love for country', 'duty to the army', and similar emotion-based lies used to trick people into throwing their lives away and inflicting harm on others.
The second is Bohumil Hrabal's 'In-house Weddings.' The book is a testament to how art and personal happiness can survive and thrive despite living under a repressive regime. Hrabal lived in Prague, the Chezh Republic during the Soviet Union years, but he made sure to make his family's and friends' lives filled with surprise, fun and pleasure.
The third one is 'The Door' by Magda Szabo. Szabo has been translated into every major language and has received several prizes for her work. She succeeds in looking back on her childhood and showing it in a light that makes the transition from being a young person into an adult very clear. It also makes a powerful statement on the importance of our parents to our lives. It is a very rich and beautiful book, full of psychological, emotional and intellectual insight.
The last one is 'The Red and the Black' by Stendhal. Stendhal's book is a coming of age book, and follows a talented young person, who rises from a no one, to a successful upcomer in the world of influence. The dilemmas, loves, doubts and decisions of the characters are very educating in a fun way: the book is immersive, engaging and helps to experience how hard it is in many situations to choose the right way.