If you’ve travelled on the subway in Toronto over the past few days, you may have noticed an odd new promotional campaign by HarperCollins Canada centred around Lawrence Hill’s The Book of Negroes and three other titles. The campaign consists of four posters, each with a simple, striking image on it: a woman’s face, a shark, a fetus, or John Lennon and Yoko Ono. There’s no text whatsoever (save a tiny HarperCollins logo in the corner), and in the centre of each image is a tiny port for plugging headphones into.

According to HarperCollins marketing manager Cory Beatty, who spearheaded the campaign, when people plug in, they’ll hear a 30-second excerpt from one of four titles “ Negroes, Steven Hall’s The Raw Shark Texts, Michael Crichton’s Next, or Jerry Leviton’s I Met the Walrus. The excerpts are followed by descriptions of the corresponding title, which run about 10“20 seconds.

HarperCollins has been working on the campaign “ one of its most expensive to date “ since last June, and the hope was that it would be the first of its kind in Canada. Instead, it turned out to be the second such campaign, as Cadbury’s beat HarperCollins to the punch in August with a plug-in ad of its own. (You could argue, though, that the concept is much better suited to promoting books than to promoting chocolate bars.) The HarperCollins campaign runs until early November.

Here are the four posters: