To learn calculus independently, several textbooks and resources are recommended, including "Calculus" by Tom Apostol, which is praised for its clarity and affordability, especially in older editions. Other notable texts include Stewart's books for practical applications, as well as Spivak, Kaplan, and Berlinski for deeper understanding. It's emphasized that a solid grasp of algebra and trigonometry is essential before tackling calculus. For effective self-study, focus on fundamental concepts like derivatives and integrals, and pace your learning to ensure comprehension. While some suggest learning alone, others advocate for finding a mentor or study group to enhance understanding and problem-solving. Libraries and used bookstores are excellent sources for affordable textbooks. Overall, the key to mastering calculus lies in consistent practice and understanding the underlying principles rather than just performing calculations.