>> Practical Security Assessment (Penetration Testing) or
How to Get Paranoid
The material will be used from different sources as well as from my own experience. However, there two particular books that you should look into if you see cybersecurity as your possible future career: Hacker Playbook 2 and Hacker Playbook 3
Also, I found that this books is a good one to get really deep and really serious into pentesting: Advanced Penetration Testing: Hacking the World's Most Secure Networks
Any methodology is not a holy grail => develop your own