Olive is just as likable as Nancy Drew, and the mystery is as thought out as an Agatha Christie one, though without quite as much mood and intrigue.
Her Royal Spyness is the first book in the Royal Spyness series. Georgie is 34th in line to the English throne, and penniless. Her half brother and his wife have "economized" and stopped her allowance, so Georgie goes to London to find a job.
There, she meets with the queen, who gives her a job: spy.