I enjoyed both TWiW and TM, and would recommend them, but they are very much of their time. If anyone is in two minds about whether to tackle Collins, then The Haunted Hotel is perhaps a good place to start, as it's very much smaller in size, but has the same odd mix of realism and way over the top (way, way over...) melodrama.
On the basis of those three books I very much prefer him to Dickens, since he doesn't have the same gallery of grotesques, his characters are more real, and his women more capable and interesting to my mind. (Not that I've read a lot of Dickens I have to confess.)
I can't actually recommend it, since I thought it was interminable, but for anyone interested in the relationship between Collins and Dickens, there's Drood by Dan Simmons. I was warned that it was long and boring, and my thoughts when I read it:
An opium-studded tour of Dickens's last years of life, as related by his best friend and apparent worst enemy, Wilkie Collins, it's most definitely long, being just shy of 800 pages, and tedium is not helped by Collins-Simmons' fixation with telling us the minutiae of Dickens' (and his family's, friends', acquaintances', enemies') life, work, parties, interests, health, hates etc etc. I can't help thinking that inside this grossly bloated book there's a slim intelligent, interesting novel desperately trying to get out.
and
I'm still plodding through Drood, the opium-induced nightmare visions of an ancient Egyptian cult and its underworld city beneath London only marginally more interesting than the immensely – and frequently bone-crushingly boringly – detailed biographies and activities of Dickens and Collins
and when I'd eventually finished, my conclusion:
An interesting and inventive book, but even as a reflection of Wilkie Collins's verbosity and hubris as narrator and Simmons's homage to Victorian-length writing, to my mind it was far too long to sustain the conceit, with its detailed itineraries and extracts from letters adding nothing useful to characterisation, background or plot. Sometimes more is too much.