Lewis' apocolyptic vision of where mankind is headed hits far closer to the mark than the more widely read visions such as Brave New World and 1984. This is because Lewis recognizes that the evil lies not in technology or even politics but in the human heart.
Lewis also shows a deeper understanding of how society functions -- as an investigative researcher I can vouch for the accuracy of his portrayal of how nefarious organizations manipulate the press, for example. He grasps what other writers never even seem to comprehend -- that it is the small choices made daily that lead down the path to Hell.
As philosophy, as social commentary, or as a rolicking good story, That Hideous Strength is a compelling read.