Heaven's Gate: America's UFO Religion by Benjamin E. Zeller takes a detailed and scholarly look at the millennial religion that made the news due to the group's collective suicide in 1997. The author treats Heaven’s Gate as a religion, not a cult. In religious scholarship, there is no fundamental difference between a religion and a cult.
For much of Heaven Gates’ history, it had more hallmarks of religion than a cult. But in the 1990s, it took a dark turn. More of the characteristics of a classic cult were enacted, like wearing ritual clothes, pooling money, control of food and sleep. Zeller wants us understand the inner reasons that made people want to commit suicide.
But by examining this group this way, from the inside, we are actually lose our objectivity. If the only moral guideline is that people believe what they are doing - there is not much more to say about the topic.