This is a brilliant horror novel, one of Campbell's best. It's a chilling story about the quality of dreams and hallucinations, and it explores the idea of "unreliable reality" to great effect, in a way that Philip K. Dick would've admired. As with most of Campbell's novel-length work, it's a slow-burn story, building a sense of creeping dread and unease throughout, increasing incrementally until it reaches its conclusion. Highly recommended. ( )