I don't know much about Robert Forward except that he wrote for a lot of TV shows, including She-Ra. That might explain a lot about The Owl. The premise is this as stated on the cover: "Alexander L'Hiboux Never Sleeps." Sounds a bit like the the idea Lawrence Block used in his series about Evan Tanner, but the execution is entirely different.
While Block's books are breezy and funny, The Owl is deadly serious. It's also very much in the style of pulp novels about The Spider and The Shadow. Al (or Owl) "wanders the streets stalking his prey, handgs out in all-night diners, and never stays in one place long enough to cast a shadow."
What the Owl does is get revenge for the people who pay for it. Two years of their salary, whatever that might be, is what he requires. Then he'll kill whoever you say needs killing if he decides to take the job. "In such cases the law is powerless. The Owl is not." Not that Al doesn't do a lot of killing of whoever needs it for free. He kills people all the time. It's best not to irritate him. After all, he suffers from insomnolence.
L'Hiboux might be schizophrenic. He narrates the story in first person, but he drops into third person all the time when he's talking about his alter ego. Of course athletes do that, too, so maybe he's not nutty at all.
The book is graphically violent from page one or two, and The Owl absorbs more punishment than any two or three or four people in other novels of this sort. Mike Hammer is a wimp compared to The Owl.
The climax of the book is really a long one, maybe not a record, but close. Over 100 pages are devoted to The Owl's assault on a cargo ship and his taking of the revenge. I was getting a little tired long before the end.
A TV movie was made from The Owl in 1991, and it must have been pretty terrible if the reviews on the IMDb are any indication of its true quality. Judging by the summary, the plot of the movie is nothing like the plot of the novel.
I suppose the novel was intended as the first in a series, but no other was published. In the U. S., at least. It seems that maybe The Owl 2 was published in England. And, God help me, I think I might order it. Somebody stop me!