I generally like Victorian novels of late and Collins was a good friend of Dickens, so perhaps it shouldn't have been that surprising, but this is a mystery novel, which in my view is a genre in which novels may be compelling and entertaining, but don't generally have that much depth or real value. And the plot did seem predictable. As it is, this book has some of the failings you might reasonably expect from a Victorian mystery novel - but also some qualities you might not expect, which I would say more than compensate. The first half or two-thirds were positively excellent, and the ending was admittedly somewhat disappointing, but only by the book's own high standards.
Next up: could be any of a dozen books, but the plan at the moment is Jared Diamond's Guns, Germs and Steel.