They have picked up the wrong book and are probably in the wrong bookstore.
I must have read the wrong book on how to beat the dealer.
There's actually one thing worse: buying the wrong book.
"Riot" is, you might say, the wrong book at the right time.
The great bane of summer reading is the feeling that you've brought the wrong books.
So they may think they have picked up the wrong book.
No sense getting all the way home only to discover she'd pulled the wrong book.
After discovering it is the wrong book, the boys go back to business seriously.
You buy something on the internet, and Amazon.com sends you the wrong books.
But I guess you've been reading the wrong books.