Kidd is currently associate art director at Knopf, an imprint of Random House. He first joined the Knopf design team in 1986, when he was hired as a junior assistant by Sara Eisenman. Publishers Weekly described his book jackets as "creepy, striking, sly, smart, unpredictable covers that make readers appreciate books as objects of art as well as literature. USA Today also called him "the closest thing to a rock star. in graphic design today, while author James Ellroy has called him “the world’s greatest book-jacket designer.” 
Turning out jacket designs at an average of 75 a year, Kidd has freelanced for Doubleday, Farrar Straus & Giroux, Grove Press, HarperCollins, Penguin/Putnam, Scribner and Columbia University Press in addition to his work for Knopf. Kidd also supervises graphic novels at Pantheon, and in 2003 he collaborated with Art Spiegelman on a biography of cartoonist Jack Cole, Jack Cole and Plastic Man: Forms Stretched to Their Limits. His output includes cover concepts for books by Mark Beyer, Bret Easton Ellis, Haruki Murakami, Dean Koontz, Cormac McCarthy, Frank Miller, Michael Ondaatje, Alex Ross, Charles Schulz, Osamu Tezuka, David Sedaris, Donna Tartt, John Updike and others. His design for Michael Crichton's Jurassic Park novel was carried over into marketing for the film adaptation. Oliver Sacks and other authors have contract clauses stating that Kidd design their books.
His novel The Cheese Monkeys (Simon and Schuster, 2001) is an academic satire and coming-of-age tale about state college art students who struggle to meet the demands of sadistic art instructors. The book draws on Kidd's real-life experiences during his art studies at Penn State. Its sequel The Learners, was released in 2008.
The author is also a serious collector of Batman merchandise which fills his Manhattan apartment. In 2001, Kidd designed and wrote Batman: Collected which features his childhood photos and several pieces from his vintage Batman collection as photographed by Geoff Spear. In the 287-page book, he writes extensively of his nostalgic memories and of Batman as a merchandising icon. Kidd is working with fellow Batman collector Saul Ferris on another book of a more particular subject matter, Bat-Manga!: The Secret History of Batman in Japan, which is scheduled for an October 2008 release.
Kidd's artistic influences are clearly "worn on his sleeve." His signature glasses are a replica of those worn by the Bauhaus designer Walter Gropius. Kidd's apartment includes cabinets showcasing his favorite book covers, signed by their authors, and display cases housing Batman memorabilia. It also has outlandish furniture such as chromed helicopter ejector seat, and along the walls are pieces by graphic designers Piet Zwart and Eileen Gray as well as comic book artists Alex Ross and Frank Miller.
Despite the wide praise of his work, Kidd has often downplayed the importance of cover designs, stating, "I'm very much against the idea that the cover will sell the book. Marketing departments of publishing houses tend to latch onto this concept and they can't let go. But it's about whether the book itself really connects with the public, and the cover is only a small part of that." He is also known to be humorously self-deprecating in regards to his work with statements such as "I piggy-backed my career on the backs of authors, not the other way around. The latest example of that is The Road, by Cormac McCarthy. I'm lucky to be attached to that. Cormac McCarthy is not lucky to have me doing his cover."