Everything I own, listen to and keep coming back to.
Linux Kernel DevelopmentRobert Love
Site Reliability Engineering, Volume 1Betsy Beyer, Chris Jones, Christof Leng, David Huska, Jennifer Petoff, Niall Richard Murphy
Systems PerformanceBrendan Gregg
Ghost in the WiresKevin Mitnick, William L. Simon
Operating Systems: Three Easy PiecesRemzi H. Arpaci-Dusseau, Andrea C. Arpaci-Dusseau