"Operating System Concepts" (aka "the dinosaur book") by Silberschatz, Galvin and Gag is a classic. It's very approachable, compares real operating systems' des

"Operating System Concepts" (aka "the dinosaur book") by Silberschatz, Galvin and Gag is a classic. It's very approachable, compares real operating systems' design choices, and covers some theory.