SFML Game Development vs SFML Game Development by Example

[JohnSnow007]

There are two books I'm reading atm:
- SFML Game Development By Example by Raimondas Pupius.
-SFML Game Development by* Jan Haller, Henrik Vogelius Hansson, Artur Moreira

I'm currently having a hard time following SGDbyExample because he's handling player inputs event by reading a text file which feels so unnatural and his variable naming is weird like "l_name" in parameters.

I've already read the SFML-GD by Jan and in both books they walkthrough different implementations of a State Manager.
Which books' code has better code implementation for their state manager and their games in general?

Should I bother learning SFML Game Development by Example's implementation of his State manager? To me, it feels more inferior to the other book. 
Someone on reddit told me to skip to Chapter 9, where they explain Entity-Component-Systems.

[eXpl0it3r]

I haven't read the SFML Game Development by Example, looking at some code online, they seem pretty similar in regards to State Manager. I think you can pick either way, or adapt it as you see fit.