It's difficult to name just one book, as there are so many fantastic works (such as the work by "our" German philosopher Immanuel Kant, which Carlo mentioned :D).
I chose 1984 by Eric Arthur Blair, better known as George Orwell, a great classic of literature that has certainly been talked about and read by many. It is a dystopian novel that describes the life of the main character Winston in a totalitarian state and how he copes with it in his everyday life.
I think it's one of the most complex works I've ever read. It unfolds a pull that I have rarely experienced and creates a fascinating and at the same time shocking world in which the power of a state stands above the freedom of the individual.
Published in 1949, this work is more topical than ever, as it reads in part like a gloomy prediction of the future. Of course, certain parallels to communism/socialism cannot be dismissed (keyword Ingsoc) and one is naturally reminded of Stalin's reign of terror and his glorified cult of personality, but I still see the work, detached from political ideologies, as a general treatment of people and how they move in a system that does not allow for individuality. The state issues doctrines that seem to promise people security as long as they conform and obey. However, Winston recognizes the treachery and contradictory nature of these doctrines, as they are highly oppressive at their core and are solely there to maintain the power of the state. In order not to jeopardize this position, the state relies on instruments of terror and surveillance, but the most dangerous instrument for me is language. It is a contradiction in terms, as it tries to eradicate them and does so with the help of contradictions that are constantly indoctrinated into you and which you cannot escape. History is washed clean, memories of the past are erased and language is cleansed of "dangerous" content. Newspeak has shown me the influence that words and the targeted manipulation that goes with them can have and the worshipful effect they can have on a society. Euphemisms and neologisms are cleverly used to create a clear image of the enemy that everyone can understand and to underpin one's own infallibility. Those who know how to use them (language in general) can steer and influence entire societies, as we see time and again nowadays, for example in political campaigns. But for me, the core of the work is simply humanity. Winston is an everyman and a clear identification figure for the reader. He wants to lead a life away from terror, away from surveillance and therefore shows himself to be nonconformist towards the various institutions. He strives for freedom and self-realization and meets someone in Julia who initially doesn't seem to fit Winston at all and yet it is she who fulfils him (if you ignore the ending). It is basic human values and qualities such as love, free development and dignity that we all identify with and 1984 confronts us with the bitter reality of decline. It is hatred that maintains power here, hatred of perceived enemies, hatred of individuality. There is simply no room for positive thoughts, and the omnipresent propaganda constantly reminds us of this with contradictions that nevertheless make us believe that the world is intact. For me, the book is a plea for cohesion, respect and esteem for people and their freedom. These are the values that we must stand up for and that enable a life that everyone should be entitled to, without restrictions. Especially in these conflict-ridden times, it is extremely important that we keep reminding ourselves of these values and support those people for whom a free and peaceful life is not possible without restrictions. That's why everyone should read this book and why I think platforms like this are so good, as they allow us to gain insights into other cultures and offer us completely new perspectives. We respect and honor each other and that should be the basis of every society.