I don't see any other replies, so I'll try. Not sure this is what's best, but it's my experience.<p>This probably depends on what subdomain you want to look at, such as networking, software patterns, forensics concerns, or even individual framework/hardware/language issues.<p>Network-<a href="https://smile.amazon.com/CompTIA-Security-Network-Fundamentals-CertBlaster/dp/1305093917/ref=sr_1_5?crid=1QEFIWHBRXVCZ&dchild=1&keywords=security%2B+guide+to+network+security+fundamentals&qid=1596035119&sprefix=Security%2B+guide%2Caps%2C530&sr=8-5" rel="nofollow">https://smile.amazon.com/CompTIA-Security-Network-Fundamenta...</a><p>Cyber security and forensics-
<a href="https://www.amazon.com/Engineer-Should-Security-Digital-Forensics-ebook/dp/B00FZHRLMI/ref=mp_s_a_1_2?dchild=1&keywords=what+every+engineer+should+know+about+cyber&qid=1596035288&sr=8-2" rel="nofollow">https://www.amazon.com/Engineer-Should-Security-Digital-Fore...</a><p>Patterns-
<a href="https://www.amazon.com/Security-Patterns-Practice-Designing-Architectures-ebook/dp/B00DNZR8K4/ref=mp_s_a_1_3?dchild=1&keywords=security+patterns+in+practice&qid=1596035349&sprefix=security++patterns+in+pra&sr=8-3" rel="nofollow">https://www.amazon.com/Security-Patterns-Practice-Designing-...</a>