Hello! Sorry for late reply - it's been rather manic at #TeamDylan these past few weeks BUT we are so very much looking forward to taking part in the show again this Sunday!
With regard to your question... Writing the prequel to the Dylan series was wonderful for us both as we knew the characters so well - after writing the other 8 books that follow to form the series. I hope our readers can see how we have also grown as writers in the last ten years.
The prequel is a chance to get to know Dylan & Jen's back-story... 'We' as readers know some of Jen's back story in the'home-life' storyline that always forms a secondary thread in all the books alongside the murders, and mayhem. But, 'we' know very little about Jack Dylan's past - until now. I should imagine it gives our readers a whole different experience 'knowing' Dylan before they read about the crimes he investigates, and what makes him the man he is...
Hope that helps!