I would like to recommend the novel Palms by Anna Hanson Dorsey. It’s the story of St. Nemesius of Rome and his daughter Lucilla. The book is based on the account that can be found in the book The Victims of the Mamertine by Augustine O’Reilly. This novel is a moving fictional account, something like Cardinal Wiseman’s Fabiola. It may be slow-moving at points, but it gives an excellent perspective on how the persecuted Church was seen in those days when Valerian was Emperor.
The book Palms is available as a free Google e-book or through archive.org, while Victims of the Mamertine can be found as a text at the link provided to archive.org.