The Door into Summer

Blurb

The Door into Summer is a science fiction novel by Robert A. Heinlein, originally serialized in The Magazine of Fantasy & Science Fiction and published in hardcover in 1957. It is a fast-paced hard science fiction novel, with a key fantastic element, and romantic elements. In three separate Locus Magazine readers polls from 1975 to 1998, it was judged the 36th, the 29th, or the 43rd all-time best science-fiction novel.
The novel was triggered by a remark that Heinlein's wife Virginia made when their cat refused to leave the house: "he's looking for a door into summer." Heinlein wrote the complete novel in only 13 days. No rewrite was needed, only some light editing that Heinlein did himself.