The following book appeared in April this year: Jaap van Oosten - Realizability: an Introduction to its Categorical Side Studies in Logic 152, Elsevier This book is a monograph about the effective topos and related toposes. The book is intended to provide advanced undergraduate students and Ph.D. students with a concise introduction to the effective topos. Contains introductions to partial combinatory algebras, tripos theory, construction of the effective topos. Synthesizes the existing literature, making a lot of material accessible to all readers. Many applications to recursive analysis, intuitionistic set theory, synthetic domain theory. Reviews abstract aspects of the effective topos construction. Variations are also developed, such as Lifschitz realizability, Modified realizability, Kleene-Vesley realizability. For Preface, Introduction and Table of Contents see: http://www.math.uu.nl/people/jvoosten/boekbegin.pdf