First ‘adult’ SF was the Day of the Triffids but my local library was very well stocked for, what was then, fairly new SF aimed at kids/teens. I’d already read books by e.g., Nicholas Fisk, HM Hoover, Sylvia Engdahl, Andre Norton and Ray Bradbury short stories. Also the 1970s Doctor Who books.

I was thinking of Marge Piercy too. I read ‘Woman on the Edge of Time’ as a teenager at least twice and re-read it this year, in my late 50s. I found it a much harder read this time, but still excellent and so prescient on communication technology.