Robert A. Heinlein is the third, and most important, of the three novas to hit the SF field. He appeared in 1939 with the publication of his story "Lifeline". In 1941 he was guest of honor at the World Science Fiction Convention in Denver. In essentially zero time, he went from being unpublished to being the dominant writer in the field. Nobody else will ever be this important in the field again, because there's now just too much of the field around for any one person to dominate the way Heinlein did.
Heinlein is one of my most important, and most re-read, authors.
I do regret many of his later books, especially The Number of the Beast and The Cat Who Walked Through Walls. But even his bad books are very readable.