Well yeah, the point is not to make _literal_ sense, this whole book is fiction, not technical writing. It's OK in that context to use devices like hyperbole and irony. A previous author, can't remember who and don't feel like googling, wrote a line in a similar spirit: "Hell is empty and the devils are here". He didn't mean that there were actual demons walking around on earth, who had left a physical place named Hell, which was at the moment unpopulated.