The events in the Poldark novels are mostly fictional. They are set against a historical canvas, yes. We can see real - world elements like the economic situation of Cornwall due to mining. But the core events such as Ross Poldark's adventures, his battles, and his romantic entanglements are all fictional. The author has simply used historical knowledge to create a fictional world full of intrigue and drama.
The Poldark novels are not entirely based on real history. While they use the historical backdrop of Cornwall in the 18th and 19th centuries, with things like the mining industry and social hierarchies of the time as part of the setting, the main events involving the Poldark family and their personal relationships are fictional. For instance, the love stories and family dramas of Ross Poldark are the product of the author's creativity, not real historical happenings.