Achieving a balance between theory and practice, this text presents the foundational topics of distributed systems and their relationships to real-world applications. With a set of exercises featured in each chapter, the book covers system models, correctness criteria, and proof techniques. It also presents numerous important paradigms in distributed systems, including logical clocks, distributed snapshots, deadlock detection, termination detection, election, and graph algorithms. The author addresses failures and fault-tolerance techniques in diverse applications, such as consensus, transactions, group communication, replicated data management, and self-stabilization. He also explores real-world issues, including distributed discrete-event simulation and security, and sensor and peer-to-peer networks.