I read Diane not long after I’d gone back and read Stan Lee and Steve Ditko’s original Spider-Man run. Both are comics. They didn’t feel like the same kind of thing.
Newspaper comics are episodic by design
A comic strip resolves itself in three or four panels. The Sunday strip gets a little more room, maybe a full page, but the shape is the same: setup, complication, punchline, done. Nothing that happens in Monday’s strip needs to matter on Tuesday. That’s not a limitation, it’s the format working as intended — a strip has to run in a newspaper every day for years, and a reader has to be able to pick it up on any given morning without having read the one before it. Even when strips get collected into books, the book is still built out of individually resolved units. You’re reading a pile of short stories, not one long one.
Comic books built continuity into the format
Reading the original Spider-Man issues, the difference from a strip shows up fast. Each issue still stands alone, on a monthly schedule, but the stakes and relationships carry forward from one to the next. Peter Parker’s problems in one issue are still his problems in the next. That’s a step toward continuity that a strip was never built for, but the format is still segmented — you feel the seams between issues, and the drama resets its intensity each time a new one starts.
The graphic novel finishes the shift
A graphic novel is a fictional story told in comic-strip format and published as a single book with one continuous story arc. No monthly reset, no requirement that a reader be able to start anywhere. Getting to that point took most of the 20th century — comics moved out of strip syndication and single-issue serials and into something that could sustain a novel-length, multi-arc narrative the way prose fiction always could. Diane is what that evolution produces: a story with the same beginning-to-end shape as a novel, just told in panels instead of paragraphs.
The difference isn’t degree, it’s design
Reading Diane right after going back to Spider-Man made the comparison obvious in a way it might not have been otherwise. A strip, a serialized comic book, and a graphic novel aren’t three points on the same scale of “how much story.” They’re three different jobs the comic-strip format was built to do, at three different points in its history.