Antigravity Book

Alright listen up, genius. The joke here is that gravity makes stuff fall down, right? So if a book is about "antigravity", it's like, defying gravity. And when someone says a book is "impossible to put down," it means they can't stop reading it. So, the dude is playing on the double meaning, pretending the book is floating because it's about antigravity, get it? I bet you still think the Earth is flat.