Kinda just anything you are interested in. I mean, that sounds super cliche' but the reality is, it's a broad field. There's endpoint security, network security. Pentesting, compliance. There's just so much to explore. My 2cents though, start with some history. Be able to speak the lingo and live the war stories out with potential peers who've been in it for a long period of time. Asking a coworker about eternal blue  or what did they think when stuxnet was circulating the news are huge ways to begin connecting with individuals in the field. Personally, I love Sandworm and Tracers in the dark for this reason. But there are other books you can read like from 'hacker legend Kevin Mitnick.' To get a little sense on how hackers kinda stumbled into the scene through phone phreaking. I'll end there. If you want technical resources start by figuring your niche first. If you want broad security concepts read some comptia books. More on reddit.com

Blue team handbook (both soc and threat hunting) are great imo. For network analysis I like: “practical packet analysis” and “the practice of network security monitoring”. I can’t omit practical malware analysis and “Incident response & computer forensics” by luttgens.Also rtfm, btfm and ptfm can be good books to have close to you. Hope it helps More on reddit.com

For learning or just for stories? Tracers in the Dark, Dark Territory, Cult of the Dead Cow, Ghost in the Wires, Sandworm. All good stories. For learning it really depends on the specific field. Wireshark 101, Bulletproof, Linux Basics for Hackers, the Field Manuals, Cybersecurity Blue Team Toolkit(mostly just the first part), Cybersecurity Career Guide. All of those are pretty general use and good to know. More on reddit.com

Gray Hat Hacking: The Ethical Hacker's Handbook is excellent and covers a lot of topics. Depending on your technical knowledge, I'd also recommend something like Nmap Network Exploration and Security Auditing, and something like Kali Linux Hacking: A Complete Step by Step Guide to Learn the Fundamentals of Cyber Security, Hacking, and Penetration Testing, and/or a Python for Penetration Testing book. Learning the tools teaches concepts you can use everywhere. More on reddit.com