I sometimes see great variations of layout/design quality between different RPGs. For example, Edge of the Empire, Shadowrun 5, or the recent OVA have great layouts and designs. Some others ... less so.
I have been trying to examine the differences between good layouts and less good layouts, but I feel like I must not be the first one, and there must be some tutorial or advice out there.
I am aware of this question about design software (as well as its little sister), but I am asking specifically about learning RPG layout design (I am actually a graphic designer and have more than enough design software already).
Similarly, I use the Graphic Design StackExchange and the UX Stack Exchange frequently enough, but even though I know I can find great design advice there, I am specifically looking for design advice for RPGs.
I have actually done layouts for non-RPG books already. But applying the same rules than for non-RPG books doesn't give great results. RPG books actually have in my opinion some of the best looking layouts out there, way better than most books and ebooks. Why?
Assuming I had a fully written RPG book, or want to redesign a poorly designed one, where could I find advice and tutorials?