Martin (updated by others and edited by Ravi Zacharias) wrote the granddaddy of all tomes on the cults in 1965. This edition is updated to 2003 and necessarily so. Martin treats each group thoroughly from its history, through its growth and on to its doctrine. Others have added more current information. This book is not for the faint of heart--the section on Mormonism, for example is 79 pages. His perspective is almost completely from showing the doctrinal aberrations of each group as compared to the Bible. He does not often do more than mention psychological and sociological aspects of control which are frequently if not always an integral part of a cultic group.
For anyone interested in understanding cultic groups so as to share Christ with them more effectively, this is the first book to have for your library.