The discussion centers around the effectiveness of various calculus textbooks, particularly Thomas' Calculus and its older editions compared to newer versions and other texts like Stewart's and Simmons'. Many participants express a preference for the older editions of Thomas' Calculus, citing their clear explanations and intuitive approach to concepts, while noting that newer editions have changed significantly and may not offer the same quality. Stewart's book is acknowledged for its diagrams and problem sets, but it receives mixed reviews regarding its rigor. Some participants recommend Simmons' book for its balance of theory and application, while others suggest Gilbert Strang's text as a viable option. The conversation also touches on the challenges of transitioning to more rigorous texts like Spivak and Apostol, which are deemed too advanced for beginners. Overall, the consensus leans towards the older Thomas editions as a solid choice for introductory calculus, while cautioning against newer versions and emphasizing the importance of selecting the right book for one's learning style.