For more understanding of critical cyber threats and hackers, I advise you to read the following:

1. “Cybersecurity - Attack and Defense Strategies: Counter modern threats and employ state-of-the-art tools and techniques to protect your organization against cybercriminals” by Yuri Diogenes and Dr Erdal Ozkaya
2. “The Hacker Playbook 3: Practical Guide to Penetration Testing” by Peter Kim
3. “Cybersecurity: Protecting Critical Infrastructures from Cyber Attack and Cyber Warfare” by
4. Thomas A. Johnson (Editor)
5. “Hacking: The Art of Exploitation” by Jon Erickson
6. “Penetration Testing” by Georgia Weidman