The Galaxy Book is a legendary relic and an eponymous object featured exclusively in Power Rangers Lost Galaxy. This magical tome has the power to open and close the path to the legendary Lost Galaxy.
The creation of the Galaxy book is unknown, it was said to have been stolen and lost many times for many centuries passed. The book is purported to hold immeasurable power and knowledge of several subjects, including the Lost Galaxy itself. It also contains information regarding the Galactabeasts (also now known as the Galaxy Megazords) and their lost counterparts, the Shark (Zenith Carrierzord), Phoenix (Stratoforce Megazord) and Rhino (Centaurus Megazord) Galactabeasts.
Somewhere between earth and the Yarolian galaxy, the space colony of Terra Venture received a distress signal from an unknown species, requesting immediate help. Commander Stanton sent a squad of GSA soldiers (chief among them, Mike and Leo Corbett) to the derelict ship and it was there the Galaxy Book was discovered on the corpse of an alien. To compound matters, the creature that may have attacked the ship, attacked and captured Mike's squadron in an attempt to reclaim the Galaxy book from Leo.
A second attack resulted in Leo losing the book, which falls out of his backpack over a railing, when he is attacked by the creature and saved by Mike. After rescuing the rest of the squad from the lower levels of the ship, Leo reclaims the Galaxy book (hidden on another alien cadaver) which triggers another attack from the creature. Leo and Mike lead the creature away from the others during their escape and eventually regroup with the others on Heliship as the abandoned ship explodes.
The Galaxy book became a top priority of the Science Division, however, the text of the tome is of an unknown language and most of Terra Venture's computers could not decode it. As such, Kendrix Morgan served was one the biggest contributors to the translation of the book's text, learning of the three missing Galactabeasts (and their true identities later on during their enslavement to Deviot). At one point, Trakeena took an interest in the Galaxy Book, enlisting the help of a monster named Rykon to impersonate a friend of Maya's, Shondra, in order to steal the book. However, her plans are thwarted when Maya discovers his ruse.
Later, Kendrix learned of an ancient weapon called the Savage Sword, a blade which is said to be stronger than all the Quasar Sabers combined. Psycho Pink (who survived the battle against the Space and Galaxy Rangers), infiltrated the colony's computer systems and absorbed the information from Kendrix's mind. Kendrix and Cassie give chase and arrive too late to keep her from obtaining the sword. Psycho Pink bests both of them and destroys Cassie's morpher, using its energy to heal herself and mutate. Kendrix chooses to enter the vortex created by the sword and morpher to save Cassie and Terra Venture. She dies in the process of destroying the sword, but saves Cassie's morpher and the colony as a result. After her death, the Science Division continued to research the contents of the book, eventually leading to the discovery of the Keonta Spell.
The first recital of the spell triggers the arrival of the Guardian of the Galaxy Book, who tries to steal it from the Science Division. After he was captured and arrested, the Guardian enlists Kai Chen's help in recovering the book, in order to prevent the future he foresaw happening. However, the untimely arrival of Deviot leads to the death of the Guardian and the capture of the Galaxy Book. Deviot completes the Keonta spell, mutating into a horrible monster and pulling himself and the colony into the Lost Galaxy.
Leo Corbett and Kai Chen read the first part of the Keonta spell in reverse. The book released a burst of mystical energy that knocked them over and vanished, becoming a portal out of the Lost Galaxy. Terra Venture and the Astro Megaship manage to escape at the cost of the Magna Defender's powers (wielded by Leo's brother Mike), when Mike forces the closing portal back open with the Torozord so the others could escape. The colony escapes the Lost Galaxy, but is pursued by Captain Mutiny, who is promptly destroyed by Trakeena. Leo eventually finds his brother drifting through space and brings him back to the colony.