Esta é a série Demonata de Darren Shan .
A série gira em torno de três crianças (citando a Wikipedia):
The series centers around three protagonists: Grubitsch "Grubbs" Grady, Cornelius "Kernel" Fleck and Bec MacConn. Although they meet each other at various points, they are from separate times; Grubbs lives in the present day, Kernel in the 1970s and Bec in around 450AD.
E é sobre um longo conflito com um universo demoníaco paralelo:
The books detail their fight against the evil demon master Lord Loss, his many demon familiars and the mysterious Shadow, who promises to destroy the human universe and to even stop death. Together with The Disciples, the main characters thwart the Demonata's attempts at world destruction multiple times.
O texto que você cita é do décimo e último livro Hell's Heroes:
Clearing my throat, to a chorus of good-natured groans from Kernel and Bec, I chant solemnly. “In the beginning Grubbs created the heavens and the earth, and everything was dark. Then Grubbs said, ‘Let there be light!’”
And there was light.
Coolio!