I'm not sure which particular store you're referring to. But as I mentioned before, big retailers like Amazon usually have a good selection. If it's a local bookstore, it depends on their inventory and how much they focus on audio books.
I think 'Ross Poldark' is very popular. It has a strong hero in Ross, and the vivid descriptions of the Cornish landscape and the mining community are really appealing.
You can try your local library. They often have a collection of books on CD, and there's a good chance they might have the Poldark novels in that format.
The Poldark novels are fiction. They are set in Cornwall during the late 18th and early 19th centuries, which gives them a historical backdrop. However, the main plotlines, the relationships between the characters like Ross Poldark and Demelza, are fictional constructs. The author, Winston Graham, used his knowledge of the time period to create a vivid fictional world that has elements of the real Cornwall at that time, but overall it is a work of fiction.
The person behind the Poldark novels is Winston Graham. His storytelling and character development in these novels have captured the hearts of many readers.