"Mathematical Methods of Classical Mechanics" by V.I. Arnol'd is praised for its beauty and depth, offering a rigorous mathematical framework for classical mechanics. It is considered more challenging than Goldstein's text and is recommended for graduate-level studies. The discussion highlights that Arnol'd's book is not ideal for beginners; prior knowledge from texts like Goldstein or Calkin is suggested for a solid foundation. While some view Arnol'd's approach as a different conceptual perspective rather than merely adding rigor, caution is advised against overemphasizing his methodology. Overall, the book serves as a complement to more introductory texts, enriching the understanding of advanced mechanics.