Good books for beginners and experienced practitioners alike:
Zen Mind, Beginners Mind, by Shunryu Suzuki
This book is a classic that introduced many people to Buddhist practice. It contains short, edited talks by the late founder of San Francisco Zen Center that are easy to read while providing profound teachings.
The Miracle of Mindfulness, by Thich Nhat Hanh
This is another classic book about Buddhism, written by a Vietnamese monk who was nominated by Martin Luther King, Jr. for the Nobel Peace Prize. Of his many books, this one has been the entryway for many people into Buddhist practice.
Taking the Path of Zen, by Robert Aitken
Aitkin-roshi began his Zen studies while in a Japanese concentration camp during World War II. His years of practice have yielded many excellent books. This is a good one to start with, as it gives an introduction to many Buddhist concepts and practices in straightforward language.
Buddhism Plain and Simple, by Steve Hagen
A dharma heir of Katagiri-roshi, and the editor of Katagiri's two books, Hagen provides a clear, down-to-earth, accessible discussion of awakening. In this book, he skillfully guides the reader through "the practice of being aware, right now, every day."
Everyday Zen, by Charlotte Joko Beck
This book by American Zen master Joko Beck is a profound source of day-to-day wisdom. She discusses a wide range of practical applications of living the dharma in daily life, using language and examples that are very accessible for Western students.