I wanted to recommend The Kingdom of the Cults by Walter Martin, which exists in an original, revised, expanded 2019 and concise Handbook form. The book's outlook is fundamentalist and evangelical. Although I am a Calvinistic Baptist and Martin was not I don't find much in the book's understanding of Christian orthodoxy I disagree with. He is fair to his subjects, while he obviously disagrees with them and is emphatic in defending his view of the gospel he is not mean spirited or dishonest.
I don't know what the legalities of it are but many Ministries put pdfs of the Hank Hannegraff revised edition in pdf format online. It is my understanding that Walter Martin's estate does not oppose this, though the newer version are still under copyright (formerly published by Ravi Zachariah until he was expunged from the cover and contents). So if you do choose to download the older versions I don't think you're offending the copyright holders.
Apologia Studios have a series called 'Cultish' which I also like. Martin's book is 50 years old and I know groups like Apologia and James White have done further research into non-Christian and non-Orthodox groups. I would love to see a self-consciously Reformed version of Martin's book.
I don't know what the legalities of it are but many Ministries put pdfs of the Hank Hannegraff revised edition in pdf format online. It is my understanding that Walter Martin's estate does not oppose this, though the newer version are still under copyright (formerly published by Ravi Zachariah until he was expunged from the cover and contents). So if you do choose to download the older versions I don't think you're offending the copyright holders.
Apologia Studios have a series called 'Cultish' which I also like. Martin's book is 50 years old and I know groups like Apologia and James White have done further research into non-Christian and non-Orthodox groups. I would love to see a self-consciously Reformed version of Martin's book.