Here's a breakdown:
* "Throw the book" refers to the practice of applying all the rules and regulations in a book (like a law book) to a situation.
* "At him" indicates the person who is being punished.
Example:
* "The judge decided to throw the book at the defendant for his crimes, giving him the maximum sentence."
Similar Idioms:
* "Give someone the full treatment"
* "Go all out"
* "Leave no stone unturned"
In essence, "throw the book at him" implies a severe and uncompromising response to someone's actions.