You have to be a little crazy to read as much into “Psycho” as David Thomson does in “The Moment of ‘Psycho’: How Alfred Hitchcock Taught America to Love Murder.” Not that crazy people can’t be charming and erudite, just as Anthony Perkins’s Norman Bates is in that movie. But read this book in long stretches — sit, as it were, with Thomson in a room and listen to him expound — and you may start having that “I gotta get out of here” feeling.

Thomson, a noted film critic and the author of “A Biographical Dictionary of Film,” isn’t really crazy, of course, just knowledgeable. His vast storehouse is on full display here, in honor of the 50th anniversary of the release of “Psycho.” (It opened in June 1960.) He skillfully locates the movie in Hitchcock’s oeuvre, linking its theme of the dangers of loneliness to “Rear Window” and “The Birds” and its voyeurism to “Strangers on a Train” and others. And, in a chapter called “Other Bodies in the Swamp,” he traces the influence of “Psycho” on more recent movies.

“Psycho,” for instance, included a toilet-flushing scene that had censors all worked up; in 1974, Francis Ford Coppola’s film “The Conversation” had a malfunctioning toilet. “The overflowing toilet is a clear reference to ‘Psycho,’ ” Thomson writes, “as well as an admission that the censors have all gone home.” More important, there was the violence of the notorious murder-in-the-shower scene, which he sees as paving the way not just for gory films like “Bonnie and Clyde” (1967) but also for the far less grim James Bond movies. How so? “Hitchcock,” he writes, “was a point of reference in the discovery of a tone that would let the audience laugh at things that were once beyond laughter because of cruelty or sexual exploitation.”

Before getting down to the business of the book’s subtitle, though, Thomson indulges in an almost frame-by-frame analysis of “Psycho,” paying particular attention to the first half, up to the point when Marion Crane (Janet Leigh) takes her fatal shower. Sets and facial expressions are painstakingly described; interior monologues are presumed; viewer reaction is postulated; tangents that take us to other movies (“The Maltese Falcon,” “To Catch a Thief”) are followed.