Dozens of Square Enix companion books have been produced since 1998, when video game developer Square began to produce books that focused on artwork, developer interviews, and background information on the fictional worlds and characters in its games rather than on gameplay details. The first series of these books was the Perfect Works series, written and published by Square subsidiary DigiCube. They produced three books between 1998 and 1999 before the line was stopped in favor of the Ultimania series, a portmanteau of ultimate and mania. This series of books is written by Studio BentStuff, which had previously written game guides for Square for Final Fantasy VII. They were published by DigiCube until the company was dissolved in 2003. Square merged with video game publisher Enix on April 1, 2003, to form Square Enix, which resumed publication of the companion books.