Read the book, The Magus.  I still think about it from time to time.  I have never seen the film.  It is a very unusual plot, mysterious, and unsettling.  The author presents a mystery of sorts, leads you on a wild goose chase, and in the end unravels it for you, but still leaves you with a feeling of doubt that anything has been explained....nearly like you wasted your time reading it, but you get sooo involved with the thing, it's amazing. I remember not being able to put it down. 

Now I think I'll try to find a copy and read it again.  We're talking like High School when I read it. 

As for the movie, I'd like to give it a try.  Love Michael Caine.  He's "da man".   Have you seen the Quiet American?   I think he did that one in 2000.  Mystery/suspense thing set in Viet Nam, around the time of Dien Bien Phu (actually just prior, I think the dateline was 1952).   The film is Bien Fou....stars Michael and Brendan Fraser (whom I never thought could act..), and some gorgeous Vietnamese woman.  Love triangle, someone gets killed...great scenery.  Shot on location.