Code Lyoko: The Adventure Begins is the first Code Lyoko book and, to date, the only one published in English. It was originally published in France as "Code Lyoko: L'Aventure Commence". This book was written as an adaptation of "Teddygozilla" and "Plagued" in comic format, using screenshots from said episodes. It also has some bonus features, one of which mentions Franz Hopper.
There are a number of errors in the English edition of the book: Sissi's name is misspelled "Sissy", Odd says "Laser Dart" instead of "Laser Arrow". Franz Hopper is called a former student, not a teacher. This last one may or may not be actually correct, given Kadic Academy's age.
The Adventure Begins' successor is The Adventure Continues.