In the book, Jackson ist the grandson of Dr. Jekyll und Mr. Hyde, making him ein third generation monster. The chemicals used by Dr. Jekyll were apparently very toxic und clung to the DNA, passing the condition down to sein progeny. The condition afflicted Jacksons Vater und drove him mad, despite sein Mutter's attempts to help. The only ray of hope Mrs. Jekyll could see for her son was that the change had stabilized through the generations, becoming less violent und unpredictable than its previous forms. als ein biochemist, sie surmised that the chemical had mutated into ein more stable state.
Jacksons condition manifested around the age of 13 or 14. Due to the prejudice faced by monsters from humans, sein Mutter protected him by keeping the truth about the family hidden. In the book, Jacksons physical change ist more mental than physical (although in the second book Hyde gains ein physical appearance of sein own, having lighter hair und different colored eyes) und ist governed by temperature rather than night und day. When Jackson gets too hot, Holt Hyde emerges, und Holt disappears when er gets too cold.
Er hat ein major crush on Frankie, whom er refers to als "Firecracker".
By the zweiten Band, DJ/Holt hat lost sein interest in Frankie, saying that they should see different people. Frankie having not seen DJ/Holt for quite ein while, because Jackson was preventing sein 'visits' by using ein mini fan to keep him cool, DJ/Holt was unaware of Frankie's relationship mit Brett (by the second book they are dating). Frankie was relieved to hear er lost interest in her. sie had feared DJ/Holt would be mad at her for abandoning him for Brett.
Though Holt wasn't directly seen in the third book, but when sein Mutter got fired, they moved to another town, where DJ was the main personality.
Er wasn't seen in the vierten Band until the last Melody chapter, where er became ein roadie for Leadfeather.