Here is an excellent beginner book from Tibetan Mahayana tradition:
The Path To Awakening
> Mind training is a comprehensive practice that is suitable for all types of students. It contains the entire path and does not depend on a person's background. Mind Training nurses and cultivates the Buddha Nature, that pure seed of awakening that is at the very heart of every sentient being. It has the power to transform even egotistical self-clinging into self-lessness. Put into practice diligently, it is enough to lead you all the way to awakening.
If you are interested in the way of Tibetan Buddhism of Mahayana tradition, then I would suggest two books to start with:
Way of Tibetan Buddhism
The Path to Awakening
> In The Path to Awakening, Shamar Rinpoche gives his own detailed commentary on Chekawa Yeshe Dorje's Seven Points of Mind Training, a text that has been used for transformative practice in Tibetan Buddhism for close to a thousand years. Clear, accessible, and yet profound, this book is filled with practical wisdom, philosophy, and meditation instructions.