Nowadays, a significant number of applications require the organization of data elements which contain at least one spatial attribute. Space support in databases poses new challenges in every part of a database management system and the capability of spatial support in the physical layer is considered very important. This has led to the design of spatial access methods to enable the effective and efficient management of spatial objects. R-trees have a simplicity of structure and, together with their resemblance to the B-tree, allow developers to incorporate them easily into existing database management systems for the support of spatial query processing. This book provides an extensive survey of the R-tree evolution, studying the applicability of the structure and its variations to efficient query processing, accurate proposed cost models, and implementation issues like concurrency control and parallelism. Based on the observation that ``space is everywhere", the authors anticipate that we are in the beginning of the era of the ``ubiquitous R-tree" analogous to the way B-trees were considered 25 years ago. Written for database researchers, designers and programmers as well as graduate students, this comprehensive monograph will be a welcome addition to the field. The book successfully integrates research results of the last 20 years, in a clear and highly readable manner. It is the first book dedicated to R-trees and related access methods, and I believe it will be valuable as a reference to everyone interested in the area. Prof. Timos Sellis, National Technical University of Athens