His comics have appeared in the New York Times Magazine, Best American Comics, and McSweeneys Quarterly. His illustrations have appeared in numerous publications including the cover of the New Yorker, the Walrus, and Canadian Notes & Queries.
He is also Lemony Snicket's partner for the new Young Readers series, All the Wrong Questions, and has illustrated and designed a new, deluxe edition of Stephen Leacock's Sunshine Sketches of a Little Town. He is the designer for several classic comics reprint series, notably collections of work by Charles Schulz, John Stanley, and Doug Wright.
Seth has exhibited throughout the world in a variety of group and solo shows. He was the subject of a solo exhibition at the Art Gallery of Ontario, which showcased the first public display of his model city Dominion. He is now a part of the Gallery's permanent collection. Dominion City subsequently toured Canada. He is the subject of a 2014 National Film Board documentary entitled Seth's Dominion.
Seth lives in Guelph, Ontario, with his wife Tania and their two cats in an old house he has named "Inkwell's End".