I have been working on this book project over a period of many years in order to create a concise but comprehensive account of exact solutions in the threedimensional Einstein theory of gravity. This theory, although tangentially related to the real gravity world, is a good model from which to extract some relevant conclusions about that world, taking advantage of simplifications due to the reduction in dimensions. Of course, after fifty years of existence, (2 + 1) gravity has been approached from many perspectives, but, to my mind, there is still no satisfactory account of solutions of physical interest. I therefore wrote the present book on exact solutions in (2 + 1) gravity following closely the pattern of the classic book, Exact solutions in Einstein's field equations with the aim of bringing to each class of solutions presented its theoretical framework, its general physical and geometrical characteristics, and references to the researchers who discovered or studied them.

I am greatly indebted to my late friends and collaborators J.F. Plebański, N. R. Sibgatullin and S. del Campo for stimulating talks. Many thanks are due to my collaborators E. Ayón-Beato, C. Campuzano, M. Cataldo, G. Gutierrez, F. Hehl, A. Macías, V. Manko, N. Mitskievich, and C. Terrero for many enlightening talks, and advice on various problems I faced when dealing with this task. This work could not have come about without a fruitful sabbatical stay at the Physics Department of the California University at Davis under the sponsorship of Professor S. Carlip, to whom I am indebted, and to UC MEXUS-CONACYT for financial support. I cordially thank my friends, particularly Y. Gurievich and M. Lopez, and colleagues from the Departamento de Física, Centro de Investigación y de Estudios Avanzados del I.P.N., for their encouragement. Many thanks to my assistant E.Vargas-Díaz for her daily support and typographical help in the final preparation of the manuscript of this book. The support of the Consejo Nacional de Ciencia y Tecnología (CONACYT), México, through various grants (at present: Grant CONACyT 178346) is acknowledged.

I really do appreciate the patience and support of my daughters, Ana Alicia and Alexandra Sofia, and sons, Sergey, Albert, Alberto-Tiko, and Alex, over all these years of writing this book.

Please do not hesitate to let me know about inconsistencies, unevenness, omissions or errors to be found in this text. Constructive comments are welcome: aagarcia@fis.cinvestav.mx.