Yeah this is a strange way to define "banned books". I would think Hustler has to be universally "banned" in all US schools, it has to be in the top 10 most banned books. Or maybe because it's a magazine Hustler doesn't count so the author left it out...

The only books I can think of that are actually banned, as in it's against the law to obtain, in the US would be like a B2 bomber capability manual or some other classified documentation.