Walter R. Martin was an American Evangelical minister, author, and Christian apologist who founded the Christian Research Institute in 1960 as a para-church ministry specializing as a clearing-house of information in both general Christian apologetics and in countercult apologetics.
I think I have read this book before, but I must have skimmed or skipped a lot of it. The only critique that I have is that I wish there were more details about the belief systems of each of these groups. However, a great and practical overview.