The Dead Secret - Wilkie Collins
Collins wrote this book not long before his classic, The Woman in White. There are some similarities - this too is a mystery story.
A secret, contained in a note dictated by a woman on her deathbed, is the central mystery in this story. Dictated by Mrs Treverton to her maid, but never passed to Mr Treverton as his wife had requested. Years later, Mrs Treverton's daughter gets to hear of the existence of the secret and is determined to find it out, though it's to her own cost.
I was particularly interested in the theme of illegitimacy in this novel, and Victorian attitudes to it, and the class to which you were born.
It's an enjoyable novel - at times too melodramatic and sentimental for modern tastes, but a great mystery, lots of suspense, and plenty of humour in some of the minor characters.