Covering host systems of accreting, relativistic bodies, and the high-energy phenomena associated with them, this self-contained astrophysics textbook is ideal for advanced undergraduates. The textbook introduces students to a unique blend of astrophysical principles, including the evolutionary history of compact binary stars, the physics of accretion and accretion disc outbursts, the observed signatures of such discs in binary stars and active galactic nuclei, the X-ray emission of accreting compact bodies, and the physics of astrophysical jets and gamma-ray bursts. Worked examples, exercises with complete solutions, full-colour figures and informative chapter summaries guide students through their studies. Boxed equations and key facts highlight important points. Produced by academics drawing on decades of experience delivering courses for The Open University and concentrating on supported learning, this textbook is an ideal guide for self-study. Accompanying resources to this textbook are available at: http://www.cambridge.org/features/astrophysics.