Radio astronomy uses unique observational techniques and offers the only way to investigate many phenomena in the Universe. This book, by two founders of the field, presents both a clear introduction to radio telescopes and techniques and a broad overview of the radio universe. In the first half of the book, we are shown clearly how radio telescopes work - from basic antennas and single aperture dishes through to full aperture synthesis arrays. In the second half, a wide-ranging and up-to-date review is provided of radio observations of our Milky Way galaxy, stars, pulsars, radio galaxies, quasars and the cosmic microwave background. Handy reviews of Fourier Transform theory, celestial co-ordinate systems and a historical outline of the subject are provided in appendices. Wide-ranging and clearly written, this book provides a thorough introduction to the subject for graduate students, and an invaluable overview for researchers turning to radio astronomy for the first time.