I’d steer clear of the Computer Graphics: Principles and Practice book as it seemed very outdated the last time I looked (admittedly a few years back). I always preferred Moller & Heyes’s “Real Time Rendering” which has a bunch of great graphics paper links on their website too.
You might want to hit up the various GPU Vendor sites too, look at their papers and techniques (nvidia developer pages, same for AMD etc) because they also have copies of older graphics text books on them. I’d suggest going over shaders and look at how shaders have developed from the early days as it might give you some perspective on the hardware. These days you tend to find shader toolsets like the material editor in UE4 rather than people writing their own shaders individually. That’s not to say it isn’t fun to try that!
Ultimately though, isn’t something you pick up overnight. So get ready for the long haul if you are really interested in it. If you just want to play around making shaders, then UE4 material editor is fine. If you really want to know about modern graphics engine techniques, well you need to start studying hard. Read papers from Siggraph, make sure you keep up with presentations from GDC, most of the AAA companies that do engine tech have some great technical papers on their sites (insomniac, valve, crytek, epic etc).