The book was better than the movie. The movie was limited by the quality of the special effects back then. But in the 60s, they were good enough to get the point across.
Another John Wyndham book was the Midwich Cockoos. Made into the movie, “The Children of the Damned”.
True, if we are watching it today. But back then...it scared the crappola outta me (as an eleven year old).