There are currently three legitimate books on exorcism;
Gabriel Amorth's An Exorcist Tells his Story
Gabriel Amorth's An Exorcist: More Stories
Malachi Martin's Hostage to the Devil.
All three of the above books are in perfect concordance with Catholic teaching and each other in the definition of possession, and the theology of possession and exorcism
Both of Peck's books, on the other hand, are bizarre anomolies which are at odds with scripture and the faith of the church fathers. Even though he pays lip service to Fr. Martin, Peck seems to believe we can battle preternatural beings through an application of human willpower.
Strange that the National Uncatholic Reporter, in it's craven hatred of Fr. Martin, trashes Peck's book- Peck actually serves their horizontal church agenda quite well.
Martin's view of the Jesuits is very much on the mark.
Scott Peck is Bill Moyers lite. Another raving liberal with zero dedication to facts.