
He means he's writing a BOOK.
The Big Bang Theory Season 11, Episode 15

like Sheldon and start their
own comic BOOK convention?
The Big Bang Theory Season 7, Episode 14

It's a comic BOOK joke.
The Big Bang Theory Season 7, Episode 13

Thank you, my lady. I'm
sure it's a fine BOOK,
Game of Thrones Season 3, Episode 5

Put the BOOK away, girl.
Game of Thrones Season 2, Episode 6