How to begin learning about NFV

After the last meeting with my supervisors, it was advised to leave the superficial exploratory phase and begin to have a serious understanding of the building blocks of the technologies that enable 5G. I will begin with NFV, since I believe it is "the most important" building block of the whole ecosystem.
But wait, where can I start?
Exploring the ETSI website to search for more specific information, there is a huge amount of documentation, with highly granular search criteria: this level of granularity is good in order to narrow down your search when you know what are you looking for. But.. when you are just beginning to learn about it can be difficult.

So, I think it is necessary to understand how the standardization body organizes the information, their internal working groups and how the documentation is released.

In the case of ETSI,

ETSI has several types of standards:

And according to history, the NFV initiative was industry motivated. Son NFV belongs to the ISG committee. Inside, there are several Working Groups (WG) each one focusing on a specific problem:

According to this, think that the documentation I am interested in has to do with the proposed use cases (SOL), interfaces and architecture (IFA), security (SEC) and the old (but relevant) management and orchestration (MAN) documents.

Still, I have to take care of something: The central topic is network slicing and its security. NFV is one of the enablers of the network slicing concept, it is important to get to know it, but I am not sure how deep I have to dig. I can be a little intense when reading, so I have to learn how to stop and not loose the main objective.