The Bodhisattvacaryāvatāra: A Guide to the Bodhisattva’s Way of Life
By Śāntideva126 pages
This epic poem on grasping firmly the intention to awaken has inspired many generations of Buddhists to live a more ethical and spiritual life and it captures beautifully the aesthetic of Buddhist ethics. Well worth reading again and again and again.
There are a few English translations of this classic of world literature. Steven Bachelor has a free translation (linked above), but I strongly prefer the Padmakara translation published by Shambhala in 1999 for its unparalleled accuracy and force.