Singularity (novel)

A sci-fi novel written by William Sleator for young adults. It was first published in 1985.

The novel is about two twins, Barry and Harry, who semi-inherit some property after their eccentric great-uncle dies. They discover that a metal shack (called the Playhouse) outside their uncle's home has a strange Year Inside, Hour Outside effect because something about that area acts as a portal to another universe.

This novel is an example of the following tropes:

 * Always Identical Twins: Barry and Harry, of course.
 * Diary: Harry keeps one while.
 * Different As Night and Day: Harry and Barry.
 * I Just Want to Be Special: Harry. He doesn't want supernatural powers per se, but he wants to be different from his brother and to step out of his shadow.
 * Improvised Training
 * More Teeth Than the Osmond Family: creature coming through a Portal Pool from another universe. It was visible from this universe long before it arrived, and the only part of it that was visible was its huge mouthful of teeth. The main character, in fact, spent a whole year waiting for the creature to arrive, knowing only its toothy appearance.
 * Out of Time, Out of Mind: Averted.  Changing his personality was his goal going in, and it works,.
 * Plot-Relevant Age-Up: Some cows wandered into the spot in the pasture where the Playhouse would be built and matured to old age overnight. Harry and Barry's uncle was also implied to have done this one night.
 * Portal Pool: When filled with water, the sink in the Playhouse shows images of another universe.
 * Red Oni, Blue Oni: Athletic, popular and pushy, Barry, is Red Oni to timid, book-smart and rational, Harry's Blue Oni.
 * Two Guys and A Girl: Harry, Barry and Lucy.
 * Year Inside, Hour Outside: Time on the "outside" passes extremely slowly while in the Playhouse.