Book Recs for lesser-known pre-2000 SF?

I've been revisiting Rebecca Ore's Alien series (published in the Ben Bova Presents series--Becoming Alien, Being Alien, and Human to Human), and it's made me think of Mary Gentle's Golden Witchbreed and other pre-2000 sci-fi.

Do you guys have any recs from that era? Not the big names, but the authors who put out a book or a trilogy or whatever that's just sort of stuck with you?