I have long had an interest in the spiritual realm. In high school I began reading books on the presence and activity of the demonic. Years later after I arrived at my first call in 1987 I found a book in the local library by Malachi Martin entitled HOSTAGE TO THE DEVIL: THE POSSESSION AND EXORCISM OF FIVE LIVING AMERICANS (1976). Although I attempted to read the book I was unable. It was simply too much. In 1996 I ran into this book again at a used book store and purchased it. I think it wasn't until I arrived at my fourth call in 2000 that I may have finally finished it. Possession and exorcism are powerful topics and sometimes difficult to study.
Recently at a local library book sale I ran across a copy of POSSESSED: THE TRUE STORY OF AN EXORCISM by Thomas B. Allen. It is endorsed on the back cover by Malachi Martin with no little praise. In short it is the account of the 1949 case of possession and subsequent exorcism that inspired the well-known move THE EXORCIST, shown in 1973 which itself was based on the 1971 novel by William Peter Blatty. The movie, however, changed the gender of the possessed and other details to protect identities, and also took some liberty with the actual facts. This book, on the other hand, is a journalist's attempt to reconstruct the events with solid facts and to present it as dispassionately as possible.
At the end the author quotes various academics who cast doubt on the truth of whether "Robbie" was actually demonically possessed. Even one of the participating priests shares this skepticism. Nevertheless, after reading Allen's account I find it difficult to dismiss Robbie's case too easily. In the end he is "cured" through the intervention of the exorcist and the repeated use of the rite; he is not cured by therapy or psychoanalysis. Robbie was also exposed to spiritualism through his aunt, culminating in the use of the Owiji Board, which continues to be sold as a popular board game. As a youth my parents also gave me one, which I also used. When my pastor suggested in confirmation its potential evil potential and that it should be destroyed, I made sure it was destroyed in the back of our garage.
The book is well worth the read for anyone interested in a well documented account of an actual exorcism, along with the book mentioned earlier by Martin. Personally, as a practicing pastor I believe in the reality of personal evil and in the possibility of possession, both of spaces and people. That said, I do not want to ever have to perform an exorcism. From all that I have read it is a draining experience.
Postscript: There is an article debunking much of what Allen wrote. You may read it here and judge for yourself. It seems credible enough, but I do not have the time at this point to scrutinize the sources or author.