Ironically, as far as I'm concerned, excellent poetry _is_ about as close as writing gets to "pure ideas" (or at the very least pure emotion). Average poetry, maybe not so much.

I think, as usual, there's a lot of nuance here. I think emotion is inextricably linked to almost all forms of communication, and that there's not such a bright line between fiction and non fiction in that regard.

The books that have taught me the most are not necessarily the ones with the most information density or even the most clarity of thought (although both help). The ones that have really conveyed their points effectively to me have all had an element of weaving them into a narrative that I could engage with, examine from different angles, absorb and remember.

But I'm also pretty sympathetic to the idea of cutting fluff at all opportunities and getting to the root of what you want to say - that's the one thing that's improved my writing the most.