5 booksOperating Systems Title Author Difficulty Priority Modern Operating Systems Tanenbaum & Bos Advanced high Operating System Concepts Silberschatz, Gagne & Galvin Intermediate high Operating Systems: Principles and Practice Anderson & Dahlin Intermediate medium Operating Systems: Three Easy Pieces Remzi & Andrea Arpaci-Dusseau Intermediate high The Little Book of Semaphores Allen Downey Intermediate high