Goblins Vs Dwarves — Philip Reeve

The reawakening of ancient sorcery is bringing new creatures to the world of Clovenstone. A network of tunnels is sneaking into the heart of goblin territory. Skarper and his friends try to halt this underground invasion, but the dwarves - ruthless, cunning and covered in mole-droppings - are a dangerous enemy. The hapless heroes of GOBLINS must defend their magical castle in a fabulously action-packed sequel from one of the master storytellers of children's fantasy fiction.