The Double Double Comics series were bound-together remaindered copies of selected DC and Marvel comics with covers taken from original DC comics or sometimes new covers adapted from interior scenes. Very hard to find in Near Mint but often show up on eBay UK in low and mid grade.
To my knowledge there are 24 different Double Double Comics across a number of titles - Action, Adventure, Batman, Detective, Jimmy Olsen, Justice League, Lois Lane, Strange Adventures, Superboy, Superman and World's Finest. But I'm still looking! Action Double Double Comics was the first Double Double Comics title from this publisher and the only one to reach 4 issues.