Synopsis: Letters between Campbell and Heinlein are in chronological order and range from the letter accompanying Heinlein's first submission to Astounding, April 10, 1939 to a 1966 Christmas card from the Heinleins to the Campbells in 1966. The letters form an extensive record of Heinlein's development as an author. His friendship with Campbell emerges as a long and fruitful one, far more nuanced and intimate than has generally been recognized. The friendship continued despite Campbell's inability to protect Heinlein from Street & Smith's erratic response to the changing publishing climate following World War II. Their paths diverged as Campbell continued to focus on producing a pulp magazine and Heinlein set out to conquer larger worlds.