Looking for Earths: The Race to Find New Solar Systems is an excellent introduction book, as a scientific story of exploration and summary of the science of planetary discovery.

Alan Boss is a planetary scientist and adviser to NASA on the search for extrasolar planets. He has had a front-row seat in the revolution over the last two decades that has led to the discovery planets outside our Solar system for the first time, leading to 215 known planets at last counting.

The book is written in an first-person style that reflects the race to discover the first exoplanets in the 1990s. He describes historical searches for planets in the early 20th Century: the hunt for evidence of planets around Barnards Stara and the meticulous work over decades of Peter Van de Kamp, a good summary of the challenges in proving the case for planets in Astronomy, and explains the techniques used to determine other planets. The heartbreaking difficulties of proving the discovery are well expressed, as well as documenting the leaders of the field at the time. Along the way, he describes the discovery of the first Brown Dwarfs, the border cases between Stars and Planets, and the bureaucratic and other challenges involved in setting up large observatories such as the Keck interferometers capable of doing this work.

This is ironic, as the first discoveries were actually made by ground-based observatories. Boss describes the race between the main teams, Geoffrey Marcy and Paul Butler of Lick observatory. The race was finally won by Michel Mayor and Didier Queloz of Geneva Observatory, who discovered the first extrasolar planet around a sun-like star, 51 Pegasi, by looking at radial velocity measurements of nearby stars. This turned out to be a close race, as the planet they had found had a short period of 4.23 days, implying the planet was what we now call a "hot Jupiter", orbiting very close into the Sun. Most teams had been looking for copies of our Solar system, looking for large planets such as Jupiter with orbits of around a decade, and had hence not started to analyse the data they had in hand, expecting to need years of measurements: examining the data showed that, had they analysed data in hand, they could have won.

Looking for Earths does a good job of explaining the field of exoplanet research as it was evolving over Boss's careeer and particularly 1995-2005, with theoretical and computer models evolving as data arrived with new puzzles. In some places, the need to give a clear explanation of a topic such as the formation of planets from solar disks slows the pace of the biography, but the book does an excellent job of describing both the science and the life lived by those doing the work. Few books I've read have offered such a good summary of the field to date, along with a good bibliography and I would heartily recommend it both as an introduction to the field and as a model for science writing.