The format of comics as we know them wasn't new, either. IIRC, early on, they used the same page size as the dime novels, which is why that size was chosen: it produced a handy product, & paper was readily available & cheap...
As for content, you really can't rule out anything. Stuff like
Katzenjammer Kids &
Blondie is probably going to happen first. (I have my doubts you get "funny animal" books at all, but IDK enough about the first strips.)
Westerns & horror/Gothic titles are very likely.
Detective titles, maybe less so; the detective story had only just been invented by Poe ("Murders in the Rue Morgue", 1841, according to the usual credit I've seen), & it would be about half a century before the likes of
Sexon Blake,
Nick Carter, & Sherlock Holmes would appear.
SF was just getting started, too, so SF comics may be latecomers, but reprints of
Frankenstein, Mary Shelly's
The Last Man (think "Omega Man"), that like, are probable.
Romance titles are also very likely IMO.
The most likely are porn comics,

not unlike the "Tijuana bibles"...
Kama Sutra, recall, was illustrated...& there was at least one magazine I know of publishing Victorian "erotica" (which is
mild by today's standards...)
The evolution from captioned panels (
Prince Valiant style) to the modern strip's conventions (everything from thought & word balloons to page structure to indicators of motion & sfx) was actually pretty rapid OTL; could be you get concurrent developments in both media.
IMO, the biggest question is literacy. Without universal education, are these books just for upper classes? And are the prices low enough the "average Joe" can read them? Are they aimed at kids, or adults? It was adult horror titles in the hands of kids, plus a flat wrong attribution of cause & effect, & purely irrational reaction to false propaganda that led to the horror backlash in the '50s; if Victorian comics are aimed at adults from the start, that never happens...