Mechanical (or aerospace) engineering. Fun/easy reading: Skunk Works: A Personal Memoir of My Years of Lockheed (Ben R. Rich) Textbook: Shigley's Mechanical

Mechanical (or aerospace) engineering. Fun/easy reading: Skunk Works: A Personal Memoir of My Years of Lockheed (Ben R. Rich) Textbook: Shigley's Mechanical Design (recent editions are by Budynas/Nisbett by older editions with Shigley as an author are just as good as an intro)