Start with high-confidence mainframe & midrange os books, then narrow by subgenre or adjacent topics.
Linux Device Drivers
Jonathan Corbet, Alessandro Rubini
Linux System Administration
Tom Adelstein, Bill Lubanovic
Ubuntu Hacks
Jonathan Oxer, Kyle Rankin
Ubuntu Linux Bible
David Clinton, Christopher Negus
Rootkits and Bootkits
Alex Matrosov, Eugene Rodionov
