Chrono Cross Ultimania
Chrono Cross Ultimania (クロノ・クロス アルティマニア?) is the official guide book for Chrono Cross, released exclusively in Japan by DigiCube, the company who also handled Squaresoft's merchandise at the time of Chrono Cross's release. Ultimania is primarily a strategy guide for Chrono Cross, featuring information typical of strategy guides for video games and RPGs, such as equipment stats, party member recruitment conditions, dungeon maps and so on; but somewhat atypically (at least for strategy guides released in the west), it also features a large amount of peripheral information on Chrono Cross, such as developer interviews, artwork, maps displaying the "geography" of Chrono Cross, and plot analysis concerning both Chrono Cross's plot as well as its connections to Chrono Trigger.
While it is generally considered an authoritative resource on most matters pertaining to Chrono Cross, it is worth noting that some of the plot information provided in this book conflicts with information Masato Kato (the director of Chrono Cross and main script writer for Chrono Trigger) has provided, so not all of the information provided in Ultimania can necessarily be treated as canonical.