Android is not just an operating system running apps, it is a living system of processes constantly communicating, competing, and failing in subtle ways. This book shows you how it really works under the surface, from Linux scheduling and memory pressure to Binder IPC and system_server control flow, so you can stop guessing and start diagnosing problems with clarity. By the end, you will not just build Android from source, you will understand how every layer interacts, giving you the ability to trace issues like jank, ANRs, and battery drain back to their true cause.