The Katha holds a special fascination for all students of the Upanishads for its happy blend of charming poetry, deep mysticism, and profound philosophy; it contains a more unified exposition of Vedanta than any other single Upanishad; its charm is heightened by the two characters of its dialogue, namely, old Yama, the teacher, and young Naciketa, the student.

Reference: The Message of the Upanishads by Swami Ranganathananda (p.2)