While "Waggit Again" is the title of the first book in the series, it is not the first book published.
The first book published in the series is actually called "Here, There Be Dragons". It was released in 2003, and "Waggit Again" followed in 2005.
So, while "Waggit Again" is the first book in the *chronological order* of the story, it was not the first book released.