 In 1957, James Blish wrote that one reason for Heinlein's success "has been the high grade of machinery which goes, today as always, into his story-telling.Heinlein seems to have known from the beginning, as if instinctively, technical lessons about fiction which other writers must learn the hard way (or often enough, never learn).He does not always operate the machinery to the best advantage, but he always seems to be aware of it."