In the UK, EU authors get paid a few pence for every loan of their books, so lending is tracked nationally. Lorcan pointed me at a Guardian article about the latest book-lending statistics which show that James Patterson (an American mystery author) was the most borrowed author in the UK last year.
Here's the list (linked to WorldCat Identity pages):
The article points out that part of the trick is being prolific. I read recently that Nora Roberts had 100 books on the New York Times bestseller list over the last ten years.
Looking at what these authors write, it's easy to see what people read: mysteries, love stories, children's books, mystery love stories, young adult mysteries, young adult love stories, and the occasional young adult Christmas paranormal love story mystery.