Even after all of their various gifts and excellences have been tallied up, the overwhelming popularity of some children’s books remains mysterious. What’s so interesting about the Baudelaire orphans? Why that particular boy wizard?

And then there’s Walter the Farting Dog. As with Captain Underpants, the secret of its success is right there in the title. Co-author Glenn Murray has often cited the book’s dedication (“For everyone who’s ever felt misjudged or misunderstood”) as the reason the book has touched a nerve, but no – it’s all about the farts.

Given the success of the first book, Kotzwinkle and Murray don’t tinker with the formula for the sequel (the second of five planned books in the series). Walter is still the beloved dog with the flatulence problem that turns many people against him, but he ultimately saves the day. Colman’s slightly grotesque digital collages are the same here, too, if a little busier. Even the little green spider that hung around in the first book shows up again in most of the scenes.

This time, Betty and Billy’s father quietly sells Walter at a yard sale when the kids aren’t looking. Walter’s new owner is an evil clown who uses a glass fart-catcher to collect Walter’s noxious gas in balloons, which he then uses to rob banks. In a moment of thoughtlessness, he lights a cigar, blowing himself, Walter, and the fart-catcher across the room. The cops catch the clown, and Walter is a hero again. (Strangely, nothing more is made of the father’s sneaky attempt to get rid of Walter.)

As with the first book, the story is slight, but the narrative is swift-moving and unpretentious. With that title, what else would you expect?