This slim volume by a Tibetan monk and meditation master is perhaps the best single volume on shamatha meditation available in English.
In 1988, in a retreat center near Castle Rock, Oregon, a group of meditators embarked on a year-long retreat devoted to shamatha or "calming the mind." The leader of the retreat, Gen Lamrimpa, gave a series of talks at the outset to set the retreatants on the right path. The talks were brief but rich in the knowledge gained from Lamrimpa's many years of solitary practice and study in the mountains above Dharamsala, India. Above all, they were practical: these were the things for a practitioner to know when embarking on a program of serious meditation.
The talks, in edited form, are reproduced here in this little book. I've been practicing shamatha off and on since 1986, and I feel as though an inestimable treasure has come into my hands. The view of the practice, the nine levels of shamatha, obstacles and antidotes--they're all here, and given by someone who has a lot of first-hand experience.
If you're interested in shamatha meditation, don't even think about it--get this book.