What to read after Ronia, The Robber's Daughter?

Ronia lives with her father, a robber chieftain, and his band of men in their fortress on the top of a mountain. On the night Ronia was born, a bolt of lightning split the stronghold in two, leaving a huge chasm - Hell's Gap - in between. Soon Ronia is old enough to explore the forest around her, but she must beware of the grey dwarfs and wild harpies that live there. One day she meets Birk, the son of a rival robber leader who has claimed the other side of Hell's Gap, and upon whom Ronia's father instantly declares war. Ronia and Birk develop a friendship that is as indestructible as the mountain fortress itself. But with their families sworn enemies they are forced to keep their friendship a secret until one fateful day when Ronia's father catches Birk . . . prompting Ronia and Birk to escape into the woods and fend for themselves. How long can Ronia and Birk survive in the magical forest? And will their fathers ever put aside their differences to get their beloved children back?