I have both books. IMO they are most valuable for the person who has less experience with & exposure to the lightweight philosophy and methods. If a lot of this type of stuff is new to you, the details and explanations are very useful. Internet postings and YouTube videos often overlook things that the author takes for granted.
One thing about the tarp book, it is 99% on the use of a beaked A-frame (Ray-Way) tarp. You will get loads of details & illustrations on using this type of tarp, but you will get almost nothing on other tarp configurations like the lean-to, flying V, or square tarp. Still, I found it useful when I first got into tarping.
I think it's safe to say that Ray's books are certainly not just expensive fluff, there is a lot of valuable info in there. Another reason I checked them out is that I read his PCT handbook looooong ago, and it was interesting to see his less strident tone in the current books. He is still a stubborn dude who thinks he's always right, but he seems to not remind people of this quite so often these days.