The book "R-Trees: Theory and Applications" offers a comprehensive examination of R-tree structures, which are crucial for the efficient management of spatial objects in database systems. It addresses the challenges associated with spatial support in databases and highlights the development and application of R-trees and their variations. The authors, Yannis Manolopoulos, Alexandros Nanopoulos, Apostolos N. Papadopoulos, and Yannis Theodoridis, provide valuable insights into the implementation of R-trees, including aspects such as cost models, parallelism, and the control of concurrent accesses. This specialized book is aimed at database researchers, designers, programmers, and students, serving as a valuable resource for anyone involved in spatial query processing and the underlying structures.