I would say Follett's Eye of the Needle is the best thriller I've ever read. He leaves Forsythe in the dust. Century Trilogy is modern; he'd been a living god for 20 years when he started it. It's meladromatic where his earlier stuff isn't. But melodrama sells, and he nails it. Try Eye of the Needle. it's short.
On the other hand, I haven't seen the film. I just finished the book a few minutes ago. Apart from the inevitable ending of the story, I didn't feel it was overly bleak. In fact, hiding underneath the initial conflict and melancholy, there was a quiet sense of hope at the heart of it all. I think this is gifted to book chiefly through the first-person narration by Bromden, which I gather was lost from the film (along with some key parts of his character development). So I can imagine that contributed to a bit of a shift in tone.