Sri Krishna gave us the essence of the Upanishads in the form of the Bhagavad Gita.
Vivekananda gave us the essence of the Upanishads as a series of lectures and books.
Some young (and old) people who find sanskrit hard and who, find the commentaries on the gita befuddling.
For them I recommend the powerful works of Swami Vivekananda. Same philosophy expressed in the language of the 20th century, easy to understand and easy to act upon.
And so powerful, and strengthening and motivating.
Those who know both Sanskrit and English can enjoy both!!