All my friend can remember is that is about a young boy's sister who is kidnapped by goblins and disappears down a tree trunk! With the help of his rabbit friend, he manages to find her and save from the goblins. My friend Jenny is keen to get that book again - what is it called?
it could be the faraway tree stories- the tree has a hollowed out trunk to slide down and people live in it. it is based on some young children who go to the tree and there are also goblins and rabbits so maybe this is it? its by enid blyton