Exoplanet research is one of the most explosive subjects in astronomy today. More than 500 exoplanets are now known, and groups world-wide are actively involved in a broad range of observational and theoretical efforts. This book ties together these many avenues of investigation - from the perspectives of observation, technology and theory - to give a comprehensive, up-to-date review of the entire field. All areas of exoplanet investigation are covered, making it a unique and valuable guide for researchers in astronomy and planetary science, including those new to the field. It treats the many different techniques now available for exoplanet detection and characterisation, the broad range of underlying physics, the overlap with related topics in solar system and Earth sciences, and the concepts underpinning future developments. It emphasises the interconnection between the various fields and provides extensive references to more in-depth treatments and reviews.