You have us the ENTIRE thing...why didn’t...this is easy
        
             
        
        
        
Answer:
It is a pun.
Explanation:
This is because it is a figure of speech that exploits a word's meaning in this case that the book was impossible to put down.
 
        
             
        
        
        
A hyphen...................not sure if is this the particular answer you are looking for though