Michael Marshall Smith is one of my favourite authors. He's written under a number of pseudonyms, including Michael Marshall, M.M. Smith, and Michael Rutger.
His horror/science fiction novels, written as Michael Marshall Smith, are my favourites. I particularly liked Spares, One Of Us, and his debut novel Only Forward. There's also a collection of short stories, What You Make It, which had some very interesting, and sometimes quite disturbing, chapters. I believe that was only published in the UK, but the chapters were included later in a much larger collection of short stories (More Tomorrow & Other Stories) which was sold outside of the UK.
I also enjoy the more "modern day" novels that he writes as Michael Marshall (The Straw Men and Blood Of Angels spring to mind. But I have to say that his horror/sci-fi novels are my favourites.
Thanks for reminding me of him, Val! I must dig his books out and give them another read.