I have read the book and I must say that this movie stays true to form. I think this is the beginning of the psychological thrillers in the same genre of Psycho. Cristina Raines gives an excellent performance as the lead, and Burgess Meredith gives an excellent supporting actor as the next-door neighbor. I have seen this movie at least twice and I think that I am going to buy both the book and the movie for my collection. The suspense just keeps building up to the climatic end, the twist you will never see coming. If you like movies like Signs and The Village, the Sentinel will be a classic prelude. Also, what is interesting is the actors in the movie-you would not recognize them if you did not read the credits. The late Jerry Orbach is great as the commercial director and Jeff Goldblum is excellent as the photographer. Also there is Beverly D'Angelo, who is underrated but great.