The Buddhist Path - A Practical Guide From the Nyingma Tradition of Tibetan Buddhism — by Palden Sherab and Tsewang Dongyal

Explanations and methods that reveal how the mind functions and what its essence is.

Introduction to the Kalachakra Initiation  by Alexander Berzin

This work explains on a practical level and in everyday language the theory of tantra, the vows, commitments, and their implications.

The Elements of Tantric Practice — by Jamgon Kongtrul - The Treasury of Knowledge - Volume 8

This volume concerns the meditative processes of the inner system of secret mantra - that of highest yoga tantra - a system of meditation that unites wisdom and compassion. The goal is to make manifest the pristine awareness that is the union of emptiness and bliss.

Creation and Completion - Essential Points of Tantric Meditation — by Jamgon Kongtrul

This work represents some of the most profound teachings of Jamgon Kongtrul with a commentary by Thrangu Rinpoche and a long, thoughtful introduction on visualization practice. Even though advanced practitioners will want to study this book, it's also designed to help beginners.

Deity, Mantra, and Wisdom - Development Stage Meditation in Tibetan Buddhist Tantra — by Jigme Lingpa, Patrul Rinpoche, and Getse Mahapandita Tsewang Chokdrub

This book contains eloquent and inspiring classic writings that lay out the central trainings on the path of Tantra. In particular, the use of visualization and sound in meditation practice. The texts included here are among the most widely studied commentaries from the Tibetan tradition.