If you like books set at the time of The Scarlet Pimpernel
then try Harstairs House by Amanda Grange
It's set on the Cornish coast in 1793, and is available in regular print, large print and audio book forms. The cover shown here is from the audio book.
Susannah inherits a house on the Cornish coast, and gladly gives up a job as a governess to claim her inheritance. But when she gets there, she finds the house has a tenant.
Oliver Bristow claims to be renting Harstairs House whilst he looks for a house to purchase in the neighbourhood, but his behaviour is odd and he disappears at times, turning up again without any explanation.
When he finds that Susannah has discovered a secret passage in the library his behaviour becomes menacing, and Susannah has to solve the riddle of Harstairs House.
I have always loved Cornwall, and I wanted to set a book on the Cornish coast. Harstairs House allowed me to bring together some of the elements I love best in romances: a large house, a mystery, a curious heroine and a hero with a past.