The 34-year-old, who has been signed up by Macmillan Children's Books, says creating the novel's main character, nine-year-old Ugenia Lavender, was "an adventure".
But she hasn't looked far to find inspiration - Ugenia gets intimidated by a princess called Posh Vactoria. And Geri insists Victoria - who was dubbed Posh Spice during her time in the chart topping girl band - is happy to be used as an inspiration.
Geri says, "Victoria was flattered and will read the book to her boys.
"I don't know yet if the other Spice Girls will be there."
But she hasn't looked far to find inspiration - Ugenia gets intimidated by a princess called Posh Vactoria. And Geri insists Victoria - who was dubbed Posh Spice during her time in the chart topping girl band - is happy to be used as an inspiration.
Geri says, "Victoria was flattered and will read the book to her boys.
"I don't know yet if the other Spice Girls will be there."