I remember reading an article claiming that The Number Of The Beast was the start of his "later, post-talented phase".
This part of the article _striongly_ reminded me of that:
In 1978, he suffered a near stroke from a blocked carotid artery that temporarily paralyzed one side of his body and left him to choose between the Damocles sword of massive seizure or the scalpel of a risky operation. He took the surgery, beat the odds, and immediately wrote "The Number of the Beast" (1980) -- four lubricious characters on a romp through various universes -- "to see if my brain would work." (Many critics said No.)
As a kid, I loved Have Spacesuit Will Travel. But even as a 14-15 year old I understood Number Of The Beast was not the same...