The House of Fantasy is built of stone and wood and furnished in High Medieval. Its people travel by horse and galley, fight with sword and spell and battle-axe, communicate by palantir or raven, and break bread with elves and dragons.
The House of Science Fiction is built of duralloy and plastic and furnished in Faux Future. Its people travel by starship and aircar, fight with nukes and tailored germs, communicate by ansible and laser, and break protein bars with aliens.
The House of Horror is built of bone and cobwebs and furnished in Ghastly Gothick. Its people travel only by night, fight with anything that will kill messily, communicate in screams and shrieks and gibbers, and sip blood with vampires and werewolves.
"The Furniture Rule", explaining the differences and similarities between the fields of weird fiction in Dreamsongs