The phrase "threw the book at" typically means to impose a severe punishment or harsh penalty. However, there are several antonyms for this expression that convey the opposite meaning. Some alternatives to "threw the book at" include showing mercy, giving a light sentence, being lenient or forgiving. These antonyms are typically used in situations where the offender has shown remorse or when the offense is considered minor. For instance, when dealing with a first-time offender or when the offense is not severe, a judge may choose to be lenient and not throw the book at them. Therefore, depending on the context, there are several antonyms for "threw the book at" that can be used to convey the opposite meaning of leniency and mercy.