The discussion centers on the need for a solid foundation in calculus after completing Calc 1 and Calc 2. While Spivak's book is praised for its approach to single-variable calculus, it does not cover the material typically found in a Calc 3 course, which includes multivariable calculus. For those seeking a rigorous alternative for Calc 3, recommendations include OpenStax resources, Apostol's volumes, and Courant's works. Munkres' "Analysis on Manifolds" is suggested as a good option, while Moise's calculus is noted for being less rigorous but suitable for average students. The importance of purchasing Spivak's book is emphasized, highlighting its value and availability online.