I would recommend "
The Woman in White" and "
The Moonstone" by
Wilkie Collins. Wonderful stories, told in an interesting manner.
If you're not already familiar with
Edgar Rice Burroughs and
H. Rider Haggard, and enjoy adventure, fantasy and sci-fi, then I'd thoroughly recommend the omnibus collections of their novels. I've enjoyed revisiting these very much - saving wear and tear on my very old paper editions
.
One of the great pleasures of choosing from MR is the care that has been taken to produce the files.