A practical guide to designing secure and energy-efficient IoT networks through cross-layer frameworks, lightweight cryptography, and machine learning-based intrusion detection, Improving Security and Energy Efficiency in IoT Networks equips readers with actionable strategies to balance security and energy efficiency in resource-constrained IoT environments. It delivers hands-on frameworks validated through simulations and hardware testbeds, covering adaptive routing, lightweight encryption, and ML-driven anomaly detection. It also includes mini-projects, review questions, and reproducible configurations for real-world deployments. Key Features:Effectively balances security and energy efficiency through cross-layer design principles. Comprehensively integrates lightweight cryptography, adaptive routing, and ML-based anomaly detection. Practically validates concepts with simulations, hardware testbeds, and hands-on mini projects. Companion resources include configuration files, scripts, and experiment notes to support reproducibility and classroom use. Ideal for IoT practitioners, network engineers, cybersecurity professionals, and researchers seeking practical solutions for secure and sustainable IoT systems. Also suited for instructors and students in networking, embedded systems, and cybersecurity courses.