Books two and three were announced as Taker of the Kraken and Sentry to the Centaurs respectively, and some sources (including Google Books) list bibliographical details for Taker of the Kraken, but neither book has been published (as of 2018) and Darlison lists Keeper of the Phoenix as a standalone work on her website.
'Can Ash and his friends rescue the village and break the evil wizard's spell in time?
'Ash Rover wants to do something important with his life. When he discovers a phoenix egg, he gets his wish. But the magical bird brings trouble to Ash's village. Soon Ash is not only the unlikely Keeper of the Phoenix, he is also on a desperate quest to save his family and friends. ' (Publication summary)