Ok, this one has been bugging me for a while now. Back in, I would say the mid-80's, I owned a hardcover book with a white dust jacket featuring a full-color photo of Saturn. I thought it was called 'The Planets' or 'The Solar System', but I haven't been able to find it under those titles. The book had one section for each planet, consisting of a nonfiction essay and a science fiction short story based on that planet. I remember in particular that Bradbury's "All Summer in a Day" was the featured story in the Venus section, but the book doesn't seem to be in the IFSDB list for that story. Thanks!
Have you already considered and rejected The Planets, edited by Byron Preiss and published in 1985? It seems to be a partial match for your recollections. It's got one essay and one short story per planet - but the Bradbury is "The Love Affair", and it's for Mars; and although one of the covers has a full-colour Saturn, the background is black, not white.