The Narrative Device

Also called the Imagination Machine, the Device is a complex arcane apparatus that allows a unique and unusual form of planar exploration. By placing a book on its lectern and powering the components with a rechargeable scepter, individuals who sit in the chairs have their minds transported to the story within the book. Their bodies remain seated and inert, but mentally (and perhaps astrally) they are able to visit times and places far away or that may not even exist in the traditional sense.
It is located in an upper story of Goblin Manor, known only to a select few scholars and staff of the Bibliopolis.
The extents and limits of travel, the permanence or inconsequence of actions performed in book realms, and the precise workings of the device are still unknown.

Upgrades to the Device

At the hands of player characters and gnomish tinkerers, the device has undergone several modifications over time. With these modifications, at the DM's discretion, objects and creatures that the characters encounter while adventuring in Book Worlds can be brought physically back with them into the Device room when the adventure in the book ends. From then on, those found objects and creatures exist in the world of Kraal, as though brought there from another plane by conjuration magic.

The Orrery of the Wanderer

The most notable alteration is the addition of the Orrery of the Wanderer to the device's own planar compass. See that page for details of this complex magic item.

Gamma Fractal

Upon resolving a particularly chaotic adventure in the Narrative Device, a new component was created: the Gamma Fractal. During any adventure in Book Worlds, each character can use the following property once per long rest:
When you roll a natural 1 on an attack roll, ability check, or saving throw, you can choose to roll another d20 and use the new result instead. Then roll on the Wild Magic Surge table in the Player’s Handbook. If the result is a spell, it is too wild to be affected by Metamagic or other class features that alter spellcasting, and if it normally requires concentration, it doesn’t require concentration in this case; the spell lasts for its full duration. Once a creature uses this property, it can't do so again until it completes a long rest.

Inventor(s)

An unidentified mage of the Bibliopolis

Complexity

The workings are highly complex and esoteric, and still largely unknown

Discovery

Procella Pergamin, Davkin, and Zaketh found the device by chance