That is false. Gerunds are verbal's that function as nouns.
Answer:
because they put in the time and effort to write the book
An example of a non-fiction memoir that represent a different culture is Angela's Ashes by Frank McCourt. The book is a 1996 memoir by Irish/American author Frank McCourt. The memoir contains many stories about Frank McCourt's childhood. The memoir focuses primarily on the author's childhood in Ireland.