The following is a passage from the Virginia Edition's Introduction to Citizen of the Galaxy by Robert James, Ph.D and William H. Patterson, Jr.
Heinlein was tackling the most serious subject he had ever written about. The idea that slavery still exists, is not a dead issue, must still be fought over and over again, was serious enough, subversive enough, that the book did not need much of the between-the-lines subversion he had been crafting into these boys’ books. Into his last few books—Double Star and The Door Into Summer - Heinlein had poured more and more of his art of pleasing. Both the editors with whom he had annoying conflicts in the past were pleased with Citizen of the Galaxy: John W. Campbell snatched up the novel’s serialization rights for Astounding; Alice Dalgliesh initially had nothing but praise: it was his “best story to date.”