S D Birkbeck: 3 books

A volcano erupts. In Upoverland scientists prepare to drop into its smoky cone. In Goneunderland rumours spread that the blast has uncovered a mass of luxite crystals. The scramble is on and as the two worlds are about to collide, Sir Ockham Bally-Ping and his team of misfit adventurers find themselves stuck in the middle.

Something is on the loose in Steaming Forest. It screeches, it scares and it kills. Where the mud boils, where the steam rises, where the giant Manglewarp Tree grows, no one is brave enough to enter the forest. In the nearby village of Pebbleknock, Sergeant Trod Elsewhere is also faced with an outbreak...

There is a land beneath our feet, a land of giant caves, simmering lakes, strange creatures and people. For centuries our two worlds - Goneunderland and Upoverland - have co-existed, together but apart. But the discovery of a legendary blue crystal of immense power threatens to put the two worlds on...