Obviously, the value of a book depends on the opinions of the person valuing it. One person can love a book that another person hates. Nonetheless, some books have stood out as generally beloved and almost universally considered great. Let me list four of my favorite classic books that I think you need to read if you have not already.
"The Catcher in the Rye" by J. D. Salinger - Despite its excessive use of profanity and its sexual parts, even many high-schools have "The Catcher in the Rye" on their reading list. And one can see why. This novel by Salinger tells a disturbingly realistic tale that highlights adolescence and teenage angst. I love most of all its underlying commentary on the resistance of growing up by teens who have already lost their innocence.
"Nineteen Eighty-Four" by George Orwell - This famous dystopian novel by George Orwell has influenced modern society and political thought greatly. For example, the phrase "Big Brother," comes from this novel. It tells the story of a futuristic society that lives under a totalitarian government. The government controls the flow of information and engages in intrusive surveillance. People may feel frightened reading it as they realize that our society still seems to be heading in that direction, even if at a slower rate than Orwell predicted.
"Of Mice and Men" by John Steinbeck - This novella won the Nobel Prize. It tragically tells the story of two migrant ranch workers in California during the Great Depression. Because of the book's short length, you can read "Of Mice and Men" very quickly. I usually read it in one night. The title appropriately comes from a line in the poem To A Mouse: "The best-laid plans of mice and men go oft awry."
"Fahrenheit 451" by Ray Bradbury - As another famous dystopian novel, "Fahrenheit 451" tells a futuristic story in which fireman burn books rather than put out fires. Ray Bradbury used the book to criticize the path of society, which unfortunately does not seem to have changed. The mostly implicit criticism of television stands out as most true, considering how "Fahrenheit 451" predicted how much television would integrate with society and the negative social impact from that.
One could make a much longer list of need-to-read books. Nonetheless, if you have not read those four books, then I highly suggest that you read them. If you have read them, then I suggest that you read them again.
Whatever you do, good luck and have fun!
