Sources
A great deal of what I know about writing and criticism, particularly regarding speculative fiction, I learned from reading Delany, particularly The Jewel-Hinged Jaw.
But one of the things I learned from Delany (from the intro to The Motion of Light in Water, I think) is how fallible memory is.
So let me try that again:
A great deal of what I think I know about writing and criticism, particularly regarding sf, I "learned" from misunderstanding and/or misremembering Delany.
Some day I really ought to sit down and re-read The Jewel-Hinged Jaw in its entirety and find out what Delany really says in it.
I highly recommend reading the book (if you can find a copy; my copy remains the only one I've ever seen) even if my memory of what it says is flawed; it contains a lot of stuff Delany wrote in (I think) his late 20s and early to mid-30s, when he was feeling his way to critical stances and to his own ideas about this sf stuff. It seems to me that the late '60s and early to mid-'70s were in general a fertile period for developing new ideas about sf; I've read a fair bit of thoughtful nonfiction written by sf writers during that time. But Delany's stuff in this book is particularly interesting.
Or at least, that's how I remember it.