Overall, this is a solid study. As a believer in hell, it was refreshing to find a study that doesn't try to dismiss the belief. Professor Gin Lum largely lets the historical evidence speak for itself.
One portion of the book that is especially compelling is the section dealing with the psychological impact of belief in hell. She notes that in being warned of hell, people “were not to act on their despair but to throw themselves on God's mercy for salvation, [but] some were unable to safely navigate the movement from anxiety to assurance” and suffered “mental breakdowns and successful or attempted suicides.”
Today, although it rarely seems to manifest itself in mental illness, the difficulty in navigating a course to the assurance of salvation remains an ongoing problem within Christianity. Belief in hell remains a formal belief in evangelical churches, but it is largely an unspoken belief, likely because of the anxiety associated with it. This is sad. Hell must be honestly faced. After facing it though, as Peter Kreeft has noted, we must look to what Christ taught about hell and our salvation from it for assurance, not to our own doubts and anxieties.