My shelves are 15" deep so I buy "Current" comic book boards, which are a smidge narrower - 6.75" wide instead of 7". This gives me enough space, with fabric wrapped around the boards, that I can fit two rows deep if I need to. To keep the back row visible, I lay the front fabric on it's side in stacks about half-high instead of standing it up. Not a perfect solution, but it works for me!