The discussion centers on various calculus textbooks suitable for self-study, highlighting the strengths of Spivak, Stewart, Apostol, and Thomas. Spivak's "Calculus" is praised for its elegant and rigorous approach, effectively conveying the subject while maintaining a narrative style. The book's problems are noted as challenging yet insightful, encouraging deep understanding. The conversation contrasts different types of mathematical texts, with Spivak's work avoiding both overly mechanical and overly simplified styles. While Spivak is favored, it's emphasized that no single book can provide complete understanding; a combination of resources is recommended for a well-rounded grasp of calculus concepts.