Mr. Hookumbacker and the Yella Yella Yum Yum Tree is a children's adventure story. The Forest of the Cracking Stone is full of wonder and natural beauty. It is also a place of magic as well as honey tickles, bumbletums, sapling shines and a kindly old tree master called Mr. Hookumbacker.

When the sapling shine Holly Shallina leaves the safety of the Forest of the Cracking Stone, she becomes trapped in the ground by the first rays of the rising sun. Holly's friends Buddy Trix, Cherry Petals and Shubbie Willows ask for Mr. Hookumbacker's help. When he agrees a race against time begins. Together they must journey far away to find a Yella Yella Yum Yum tree. Their journey takes them to a forbidden wood full of grubble wig and needle node weeds and on to the Forest of the Falling Waters. From there they must return with enough time to save Holly Shallina.