It was seen in a box of books belonging to Greg Universe that his son Steven found in his storage unit. Greg examined the books and then took Passions of Xanxor, saying he would let Steven look at it in a few years, when he gets older. While no rating is shown, the way Greg snatches it from Steven implies that it's written for adults.
The librarian in the Buddwick Public Library is seen reading the book.
- This is presumably a science fiction novel.
- It is also most likely a romance or erotica novel based on the cover art, the name, and the way Greg blushed and snatched it away from Steven.
- The cover image, with a male human apparently falling for a larger/taller female alien, mirrors the relationship between Rose and Greg.
- The cover image is also a parody of covers of real-life romance novels, albeit with the roles reversed: the man is the "damsel in distress" being held in the arms of the heroic female alien warrior.
- The cover art is similar to a lot of "pulp era" science fiction from the 1920s to the 1940s (prier to the Sci-fi Golden Age), like Planet Stories magazine. On a typical pulp sci-fi cover, it would be the man holding a helpless woman while striking a heroic pose and firing a "raygun" at some off-camera threat.
- The title might be inspired from the Barsoom story "A Princess of Mars."