The discussion centers around the book "Calculus: One and Several Variables" by Saturnino L. Salas, Garret J. Etgen, and Einar Hille. It is noted for its progressive exercises that effectively teach section concepts, but criticized for its terse explanations that often rely on dense jargon, making it less accessible for students. The consensus suggests that while the book provides a decent treatment of multivariate concepts and proves many theorems, it falls short in clarity and depth, particularly for those pursuing advanced studies in theoretical physics, such as quantum field theory (QFT). Users recommend seeking additional resources beyond this text for a comprehensive understanding necessary for graduate-level research.