Ellen G White, prophetess of the SDA Church wrote a book called "The Great Prophecy ( between Christ and Satan)". I found it a gross simplication of the History of Christianity with a prejudice against the Catholic Church. It all descends from Millerite Millennialism. I did a comprehensive course with them and enjoyed the gaudy illustrations of Daniel's symbolic statue etc. They believe the "mark of the beast" is Sunday worship and they proselytize very aggressively, not disclosing that they are Seventh Day Adventists and offering a free course on Revelations. They are accepted as Christians by Orthodox Christians because they believe in the Trinity and have a valid baptism. They do not believe in Hell and the soul as I do and have other similar distinctives to those of the WT such as a dodgy Christology. I love them and wish them well.