No matter subject you plan to major in, Carl Sagan's books will help you to prepare both intellectually and emotionally for it. If you want to pursue science, books like Pale Blue Dot will inspire your both your idealism and your skepticism. If you want to become a historian or anthropologist, Shadows of Forgotten Ancestors (co-written with Sagan's wife Ann Druyan) will teach you how to imaginatively connect with your subject matter. If you want to go into politics, The Demon-Haunted World (also co-written with Druyan) is a must-read on how to inspire action while refusing to give in to pseudoscientific ideologies. Carl Sagan's work is simply a one-stop-shop for how to be a human being: you owe it to yourself to read him!