The Constructopedia is a red book which contain vital building instructions for LEGO Island.
The Infomaniac first wrote the Constructopedia around the same time that he first built LEGO Island as a way to keep his building instructions together. Since then, LEGO Island evolved into a large town full of buildings, and many pages were added to the Constructopedia for these new buildings.
In 2001, the Brickster broke out of jail, flew to the Information Center by Police Helicopter, and stole the Constructopedia. He tore almost all of the book's pages out, and as a result every building on LEGO Island deconstructed. He let most of the pages scatter in the wind while he brought five Constructopedia pages to Castle Island and Adventurers' Island to be guarded by Cedric the Bull and Sam Sinister, respectively. The book's cover was also left on LEGO Island.
Pepper Roni explored the barren LEGO Island, collecting any Constructopedia page he found and putting it back into the book cover. As a result, the lost buildings reformed one by one. Pepper also traveled to Castle Island and Adventurers' Island to locate the pages there. In only a few days, all the Constructopedia's pages were restored, and LEGO Island was rebuilt. After that, the Constructopedia was hidden in a secret part of the Information Center to keep the Brickster from stealing it again.
The Constructopedia was filled with building instructions for almost everything on LEGO Island. The Constructopedia was actually specially tied to LEGO Island, as not only did its building instructions make rebuilding Brickster-deconstructed buildings easier, but also that the placement of its included content depends on its building instructions' place inside the Constructopedia. If the building instructions of a building are removed from the Constructopedia, the building deconstructs, and its LEGO Bricks levitate into the sky where they disappear; if the page is placed back inside the Constructopedia, then the LEGO Bricks fall from the sky and reform the building. Why this happens is not known; however, the Constructopedia can only rebuild buildings in this manner if its deconstruction was a result of its page being removed, which is why damaged buildings with pages still in the Constructopedia cannot be repaired in this manner.
- While the Constructopedia has not appeared in LEGO Island 3 itself, it was briefly mentioned in the novelization. When Pepper wondered why they simply could not use the Constructopedia to repair LEGO Island, Bill Ding explained that it could only repair buildings if the building's deconstruction was a result of a page being torn out.