Marie Claire's denim-themed August issue is arriving at subscribers' homes with an extra cover they "unzip" to open by pulling on a perforated strip.

Guess logos wallpaper the inside of the magazine's zipped-down cover, which cost the brand something in the mid six figures, said Nancy Berger Cardone, VP, publisher and chief revenue officer of Marie Claire, which is published by Hearst.

"We wanted something interactive off the cover that would create a new experience for our audience but also play into the denim theme," Ms. Cardone said. "Creating the reveal of the cover through the denim zipper seemed perfect."

August is traditionally a slow month for fashion magazines, partly because their high-profile September issues attract ad pages that might otherwise run in adjacent issues. But Marie Claire said the tactic worked for the month because it felt "authentic" to the issue and the brand partner.

"Advertisers love being attached to something that's innovative and out of the box," said Ms. Cardone. "It was high recall, high engagement."

The magazine has been experimenting with ways to take advantage of print, publishing a May issue with a fold-out "origami" cover" showing off five celebrity faces. Ms. Cardone says readers and marketers can expect more like this from the magazine.

"Once you set the bar where marketers look to you as being the place that's going to generate ideas and breakthrough advertising, the ideas flow," she said.

The denim cover went to Marie Claire's 800,000 subscribers. The newsstand version features cover star Zoe Saldana dressed in, you guessed it, denim.

Marie Claire's ad pages in the issues from January through July were roughly even with the same issues last year, down less than 1%, according to Media Industry Newsletter. Monthlies as a whole declined 6.1%.