The first one that immediately leaps to mind is Clive Barker’s The Scarlet Gospels.
The reason why this disappointed me so much is that I had been looking forward to it so much. Barker hadn’t written a horror novel in quite some time (since Coldheart Canyon in 2001, in fact). He had jumped over to doing Young Adult fantasy via his Abarat series…and then, as he had some health issues, the spaces between even those books grew longer. So when I heard that he was going to be returning to horror, I was thrilled. Even better: The book was going to feature the first ever meet-up between two of Barker’s most famous creations! His occult investigator, Harry D’amour, was going to encounter the Cenobites from the novel The Hellbound Heart (both creations appeared more famously in films based on Barker’s work — the HELLRAISER series, and LORD OF ILLUSIONS). I found out about the book in 2010. It was finally released in 2015.
…and I was majorly disappointed.
First of all, it was SHORT. Barker’s last few horror novels had been doorstoppers. Big, chunky books full of detail and character. When Barker announced The Scarlet Gospels in 2010, he said it clocked in at 243,000 words. The book that arrived on my doorstep 5 years later had apparently been ruthlessly edited down to nearly HALF that.
Second: possibly as a result of the trimming, the book read like Clive Barker fanfiction, not Barker himself. Characterization was minimal, and the plot whizzed from point A to point B, almost summarizing the events occurring in between.
It certainly wasn’t worth the five-year wait from announcement until release… much less the 14-year wait since Barker’s previous horror novel. So disappointing.