The field of concurrent computing has gained in importance after major chip manufacturers switched their focus from increasing the speed of individual processors to increasing the number of processors on a chip. The computer industry has thus been calling for a software revolution: the concurrency revolution. A major challenge underlying this paradigm shift is creating a library of abstractions that developers can use for general purpose concurrent programming. We study in this book how to define and build such abstractions in a rigorous manner. We focus on those that are considered the most difficult to get right and have the highest impact on the overall performance of a program: synchronization abstractions, also called shared objects or concurrent data structures. The book is intended for software developers and students. It began as a set of lecture notes for courses given at EPFL, Saarland University, Technical University of Berlin, and Télécom ParisTech.