Final answer:
The idea that there's one guaranteed method to measure an author or book's impact is false; impact is a complex interplay of various measurable and subjective factors.
Step-by-step explanation:
The statement, "There is one guaranteed way to determine how much impact an author/book has had," is false. The impact of an author or book can be measured in various ways, such as through sales numbers, the number of citations, academic discussions, cultural influence, awards received, and longevity of the book's relevance. However, there is no single guaranteed method to quantify the overall impact comprehensively, as it involves a complex interplay of factors, some of which are subjective and vary over time and place.