Durgnat, Raymond. A Mirror for England: British Movies from Austerity to Affluence. London: Faber and Faber, 1970. (Durgnat is critical of Powells casting of Bohm and finds him to be the films weak link.)
Finler, Joel W. Hitchcock in Hollywood. New York: The Continium Publishing Co., 1992. (Finler details Hitchcocks decision-making process for the casting of Psycho.)
Kapsis, Robert E. Hitchcock: the Making of a Reputation. Chicago: The University of Chicago Press, 1992.
Leigh, Janet. Psycho, Behind the Scenes of the Classic Thriller. New York: Harmony Books, 1995. (Although this is a fairly gossipy, insubstantial book, there are some good stories involving Hitchcocks relationships with the cast.)
Powell, Michael. Million Dollar Movie. Heinemann, 1992. (This is a great resource for information on Powells experiences making Peeping Tom and on its reception. Powell writes quite a bit on his choices in casting.)
Rebello, Stephen. Alfred Hitchcock and the Making of Psycho. New York: Dembner Books, 1990. (Rebello offers a lot of behind-the-scenes information, although his ego seems to conflict sometimes with the reliability of the information. He does say that he structured the character of Norman with Perkins in mind.)