That’s all true, but as I alluded to, if you’re not doing this as a strict training regime, you’re only doing this for fun. In which case how much effort do you want to put into learning? Studying books upon books at a time may be very time efficient, but I recall my time with the Instrument Procedures Manual was not a very exciting one (thank you, publishers of From the Ground Up). However, 6 years of learning really slowly turned out to be helpful when I went through ground school, PPL, Night, Multi, and Multi IFR training, because these pieces of knowledge are already firmly ingrained into your mind over 6 years of continuous learning.
I have a friend who’s flying on flight sim and wants to do all the cool things I do. The best way to learn is to expose him to little bits of information he needs to know for each flight, and slowly fill in the gaps here and there, rather than overwhelm him with a ton of reading material.