Oh, wow, really.

Officials can swear using any book or document meaningful to them – or none at all.

https://www.freedomforum.org/swear-bible-oath-of-office/

There’s also some actually used examples like a stack of banned books, Superman comic book, and even a Dr. Seuss book.

It seems like swearing on the Constitution should be mandatory.

Trump’s preferred book might have been too flagrant too soon

When I get inaugurated, I’ll swear on a copy of Naked Lunch.

The Cartoon History of the Universe it is.