I picked this paperback in the 1980s in a second hand bookshop but can't remember the name.
It starts with a group of teenagers going to a disco. The floor then dissolves and they wake up on a different planet run by a higher being who has brought aliens from all walks of life to see who will get to utopia or Eden. I remember the box man character who enticed beings to enter his box so he can eat them.
I remember the book had a purple cover. Also the Earth was blown up that's why the chosen teenagers ended up on the planet. Other than the box man I cannot remember a thing it's a shot in the dark but I'm guessing with the word disco rather than discoteque then late 70s early 80s.