Your kid didn't just read Dog Man. They inhaled it. They read it in the car, at dinner, in bed with a flashlight. They've read the whole series and now they're looking at you like you owe them something. You do. you owe them the next book that does what Dog Man did: made reading feel like something they chose, not something assigned.
The trick is understanding what about Dog Man they loved, because it's not one thing. Some kids loved the format (pictures on every page). Some loved the humor (absurd, gross, silly). Some loved the length (250 pages that feel like 50). Some loved the meta-narrative (George and Harold "writing" the story). Here's what to try based on what hooked your kid.
The Bad Guys by Aaron Blabey is the closest match to Dog Man in format and energy. Four villains try to be heroes. Enormous text, drawings on every page, 140 pages that read in 45 minutes. The series starts as pure comedy and evolves into a surprisingly complex sci-fi saga. If your kid hasn't read The Bad Guys yet, start here. 16 books.
InvestiGators by John Patrick Green follows two alligator detectives (Mango and Brash) who work for a secret government agency operating out of a sewer. The humor is pun-heavy (the agency is called S.U.I.T.. Special Undercover Investigation Teams) and the art is colorful and kinetic. Similar format to Dog Man but with slightly more sophisticated humor. 7+ books.
Cat Kid Comic Club by Dav Pilkey is the Dog Man spinoff your kid may not have found yet. Li'l Petey teaches baby frogs how to make their own comics, and each chapter features a different frog's creation in a different art style. It's Dav Pilkey's love letter to creativity and the meta-narrative goes even deeper than Dog Man. 5 books.
“The thing your kid loves about Dog Man isn't Dog Man. It's the feeling of finishing a book and wanting the next one immediately.

Captain Underpants by Dav Pilkey is the obvious next step if they haven't read it. same author, same universe, same Flip-o-Rama. A principal gets hypnotized into becoming a superhero in his underwear. The humor is cruder than Dog Man and the format is more text-heavy (illustrated chapter book rather than full graphic novel), which makes it a slight step up in reading difficulty. 12 books.
The Terrible Two by Mac Barnett and Jory John is about two rival pranksters who join forces at a new school. The pranks are elaborate and the humor is smart-silly (Mac Barnett and Jory John are two of the best comedy writers in children's books). Less visual than Dog Man. it's a proper chapter book with some illustrations. but the pacing is fast and the laughs are constant. 4 books.
Diary of a Wimpy Kid by Jeff Kinney is the prose equivalent of Dog Man: a book that looks easy, reads fast, and makes kids who "don't read" read 220 pages. The humor is more observational and cynical. Greg Heffley is a deeply unreliable narrator. The diary-plus-cartoons format is its own thing and it's genius. 18+ books.
Hilo: The Boy Who Crashed to Earth by Judd Winick is a full-color graphic novel about a mysterious boy who falls from the sky, shoots lasers, and can't remember where he comes from. More story than Dog Man, more action, higher emotional stakes. The art is beautiful and the pacing is relentless. Once your kid finishes Book 1, they'll want all 10.
The Last Kids on Earth by Max Brallier is about Jack Sullivan surviving a monster apocalypse from his tree house fortress. The books are illustrated heavily (by Douglas Holgate) but are proper chapter books. a meaningful step up from graphic novels. The humor is Dog Man-adjacent (gross monsters, sarcastic narrator) but the stories are longer and more complex. Netflix series tie-in. 9 books.
“The thing your kid loves about Dog Man isn't Dog Man. It's the feeling of finishing a book and wanting the next one immediately.
Narwhal and Jelly by Ben Clanton is Dog Man's younger sibling. Narwhal is joyful and enthusiastic. Jelly is a skeptical jellyfish. Their friendship is told in short comic segments with simple vocabulary and genuine warmth. These are shorter and easier than Dog Man. perfect for a younger sibling or for the Dog Man reader who wants something lighter between installments. 8+ books.
Real Pigeons Fight Crime by Andrew McDonald is about a squad of crime-fighting pigeons led by Rock Pigeon, who can transform into other things. The humor is absurd (the pigeons have names like Tumbler and Grandpouter), the mysteries are genuinely plotted, and the illustrations by Ben Wood are on every page. This series is massively popular in Australia and building momentum in the US. 7 books.
More options: Lunch Lady (Jarrett J. Krosoczka. graphic novel, school lunch detective), Press Start! (Thomas Flintham. video game-themed early reader), Babymouse (Jennifer L. Holm & Matthew Holm. graphic novel, girl protagonist), Super Rabbit Boy (Thomas Flintham), Baloney and Friends (Greg Pizzoli)