The Science Fiction Book Club is still around, there is a website somewhere
I belonged to the Science Fiction Book Club for several years in the late '60s. I still have everything I got from them, up in the attic somewhere. It is amazing how I can recall so many of the titles even though I haven't seen the books in decades. Impressionable youth, I suppose.
I remember getting 'The Past Through Tomorrow', 'The Foundation Trilogy', 'I, Robot', '2001: A Space Odyssey', and various other books by the likes of Kate Wilhelm and Harlan Ellison and Robert Silverberg and Ray Bradbury. Of course, I noticed that the paper stock and binding weren't exactly what you found in the book stores, lol.
Them were the days....