This is a very clever novel. Broadly speaking, it's the story - the diary, almost - of Mike Engleby. That's it, really. It's a murder mystery, in some ways: someone goes missing, and the book is about the reader's journey to find out what happened as much as Engleby's. I don't think that it's a surprise to learn that Engleby is a murderer - or is he? - but then the novel isn't so much about that as about how easy it was for him to conceal the fact from himself. And Engleby is an odd fish. He "wants everybody to be happy", but he steals small change (and bicycles). He dismisses his best friend as "pedestrian" but empathises with people he's never met. But all this is utterly convincing, and the degree of empathy Faulkes has for this misfit is astounding. Like Joyce, he includes nothing that Engleby does not know or experience - so we've no way of knowing what "really" happened, and the novel asks whether it even "really" matters.
Engleby is about time, and how far it is an illusion. It's about consciousness, and how easy it is to manipulate it. It's a wonderful book that I wouldn't have read if someone hadn't recommended it to me, which just goes to show: Never Judge a Book by its Cover. (Which is, by the way, truly uninspired.)