This will be a hard one. In the 90's I remember reading a book about a huge cube people were living in. I remember that there were huge rooms where different "groups of people" were living, connected by elevators that were traveling for days.
Another particular detail is that the rooms were cleared by fire when there was nobody left, and that the meat was grown in labs.
And because I was a teen at that time, I clearly remember a scene describing a blow job between the two main caracters....
The details are quite vague but I remember that there was a man and a woman running from something and that at least the woman manged to get inside one of the elevators and reach another room.
I remeber that the book was quite old when I was reading it, so the novel could be from the 70's.